Systems and methods for removing finely dispersed particulate matter from a fluid stream

ABSTRACT

Disclosed herein are systems for removing particulate matter from a fluid, comprising a particle functionalized by attachment of at least one activating group or amine functional group, wherein the modified particle complexes with the particulate matter within the fluid to form a removable complex therein. The particulate matter has preferably been contacted, complexed or reacted with a tethering agent. The system is particularly advantageous to removing particulate matter from a fluid waste stream following mining or ore processing operations.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/706,586, filed on Dec. 6, 2012, which is a continuation of U.S.application Ser. No. 12/792,181, filed Jun. 2, 2010 (now U.S. Pat. No.8,349,188), which is a continuation-in-part of U.S. application Ser. No.12/363,369 (now U.S. Pat. No. 8,353,641), filed Jan. 30, 2009, whichclaims the benefit of U.S. Provisional Application No. 61/028,717, filedon Feb. 14, 2008, U.S. Provisional Application No. 61/117,757, filed onNov. 25, 2008 and U.S. Provisional Application No. 61/140,525 filed onDec. 23, 2008; U.S. application Ser. No. 12/792,181 also claims thebenefit of U.S. Provisional Application No. 61/183,331 filed Jun. 2,2009, U.S. Provisional Application No. 61/246,585 filed Sep. 29, 2009,U.S. Provisional Application No. 61/253,332 filed Oct. 20, 2009 and U.S.Provisional Application No. 61/346,702 filed May 20, 2010. The entireteachings of the above applications are incorporated herein byreference.

FIELD OF THE APPLICATION

The application relates generally to the use of particles for removingfinely dispersed particulate matter from fluid streams.

BACKGROUND

Fine materials generated from mining activities are often foundwell-dispersed in aqueous environments, such as wastewater. The finelydispersed materials may include such solids as various types of claymaterials, recoverable materials, fine sand and silt. Separating thesematerials from the aqueous environment can be difficult, as they tend toretain significant amounts of water, even when separated out, unlessspecial energy-intensive dewatering processes or long-term settlingpractices are employed.

An example of a high volume water consumption process is the processingof naturally occurring ores. During the processing of such ores,colloidal particles, such as clay and mineral fines, are released intothe aqueous phase often due to the introduction of mechanical shearassociated with the hydrocarbon-extraction process. In addition tomechanical shear, alkali water is sometimes added during extraction,creating an environment more suitable for colloidal suspensions. Acommon method for disposal of the resulting “tailing” solutions, whichcontain fine colloidal suspensions of clay and minerals, water, sodiumhydroxide and small amounts of remaining hydrocarbon, is to store themin “tailings ponds.” These ponds take years to settle out thecontaminating fines, posing severe environmental challenges. Tailingsponds or similar liquid retention areas can contain aqueous suspensionsof fine particles from mining operations and other industrialoperations, for example fine coal particles from coal mining and fly ashfrom coal combustion, with the potential for environmental damage andcatastrophic leakage. It is desirable to identify a method for treatingtailings from mining operations to reduce the existing tailings ponds,and/or to prevent their further expansion.

Certain mining processes use a large volume of water, placing strains onthe local water supply. It would be advantageous, therefore, to reusethe water from tailings streams, so that there is less need for freshwater in the beneficiation process. In addition, certain miningprocesses can create waste streams of large-particle inorganic solids.This residue is typically removed in initial separation phases ofprocessing due to its size, insolubility and ease of sequestering.Disposal or storage of this waste material represents a problem for themining industry. It would be advantageous to modify this material sothat it could be useful in-situ, for example as part of a treatment forthe mining wastewater.

A typical approach to consolidating fine materials dispersed in waterinvolves the use of coagulants or flocculants. This technology works bylinking together the dispersed particles by use of multivalent metalsalts (such as calcium salts, aluminum compounds or the like) or highmolecular weight polymers such as partially hydrolyzed polyacrylamides.With the use of these agents, there is an overall size increase in thesuspended particle mass; moreover, their surface charges areneutralized, so that the particles are destabilized. The overall resultis an accelerated sedimentation of the treated particles. Following thetreatment, though, a significant amount of water remains trapped withthe sedimented particles. These technologies typically do not releaseenough water from the sedimented material that the material becomesmechanically stable. In addition, the substances used forflocculation/coagulation may not be cost-effective, especially whenlarge volumes of wastewater require treatment, in that they requirelarge volumes of flocculant and/or coagulant. While ballastedflocculation systems have also been described, these systems areinefficient in sufficiently removing many types of fine particles, suchas those fine particles that are produced in wastewater from miningprocesses.

There remains an overall need in the art, therefore, for a treatmentsystem that removes suspended particles from a fluid solution quickly,cheaply, and with high efficacy. It is also desirable that the treatmentsystem yields a recovered (or recoverable) solid material that retainsminimal water, so that it can be readily processed into a substance thatis mechanically stable. It is further desirable that the treatmentsystem yields clarified water that can be readily recycled for furtherindustrial purposes.

An additional need in the art pertains to the management of existingtailings ponds. In their present form, they are environmentalliabilities that may require extensive clean-up efforts in the future.It is desirable to prevent their expansion. It is further desirable toimprove their existing state, so that their contents settle moreefficiently and completely. A more thorough and rapid separation ofsolid material from liquid solution in the tailings pond could allowretrieval of recyclable water and compactable waste material, with anoverall reduction of the footprint that they occupy.

SUMMARY

The present invention is directed to systems and methods for removingfinely dispersed materials or particles from wastewater streams producedduring mining operations.

In one embodiment, the invention is directed to a method of removingparticulate matter from a waste tailing fluid, comprising: providing anactivating material capable of being affixed to the particulate matter;affixing the activating material to the particulate matter to form anactivated particle; providing an anchor particle and providing atethering material capable of being affixed to the anchor particle; andattaching the tethering material to the anchor particle followed byattaching the tethering material to the activated particle to form aremovable complex in the fluid; wherein the fluid is a waste tailingfluid derived from energy production or a mining process. In certainaspects, the mining process is coal mining or the mining of an inorganicore. In additional aspects, the particulate matter is selected from thegroup consisting of coal combustion products, coal fines, clay particlesand mineral particles. In an additional embodiment, the fluid isselected from the group consisting of red mud fluid stream, gangue,slurry containing fine particulate kaolin, tailings from trona miningand slurry produced by phosphate beneficiation. In certain aspects, theanchor particle comprises sand. In certain additional aspects, thetethering material is material is selected from the group consisting ofchitosan, lupamin, branched polyethyleneimine (BPEI),polydimethyldiallylammonium chloride (PDAC), andpolydiallyldimethylammonium chloride (pDADMAC). In some embodiments, theactivated particle attaches to the tethering material by electrostaticinteraction, hydrogen bonding or hydrophobic behavior. In some aspects,the anchor particle comprises a material indigenous to a mining process.

In an additional embodiment, the invention is a method of removingparticulate matter from a fluid, comprising providing a modifiedparticle comprising a particle functionalized by attachment of at leastone amine functional group; dispersing the modified particle within thefluid so that it contacts the particulate matter to form a removablecomplex in the fluid; and removing the removable complex from the fluidwherein the fluid is a waste tailing fluid derived from energyproduction or a mining process.

In a further aspect, the invention is directed to a system for removingcoal fines from a fluid, comprising: a fluid containing a population ofsuspended coal fines; an activator polymer added to the fluid to complexwith the suspended coal fines to form activated coal fines, theactivated coal fines residing within the fluid volume; an anchorparticle complexed with a tethering agent to form tether-bearing anchorparticles, the tether-bearing anchor particles being mixed with thefluid volume to contact the activated coal fines, the tether-bearinganchor particles being capable of complexing with the activated coalfines to form complexes removable from the fluid, wherein the complexesremovable from the fluid comprise a composite material comprisingcomplexed coal fines and anchor particles. In some embodiments, theanchor particle comprises coal. In additional embodiments, the anchorparticle comprises a non-combustible material. In yet additionalaspects, the anchor particle comprises a mineral.

The invention also encompasses a method for removing coal fines from afluid, comprising: providing an activator polymer capable of interactingwith a population of coal fines suspended in a fluid; adding theactivator polymer to the population to form activated coal fines;providing an anchor particle; complexing the anchor particle with atethering agent capable of complexing with the activated coal fines,thereby forming tether-bearing anchor particles; mixing thetether-bearing anchor particles with the activated coal fines to form acomplex removable from the fluid, the complex comprising a compositematerial comprising coal fines and anchor particles, and removing thecomposite material from the fluid. In some embodiments, the anchorparticle comprises coal. In additional embodiments, the anchor particlecomprises a non-combustible material. In some embodiments, the anchorparticle comprises a combustible material. In yet additional aspects,the anchor particle comprises a mineral. In certain other aspects,anchor particle comprises a starch particle. The invention additionallyencompasses an energy-bearing pellet produced according to this method.In some aspects, the energy-bearing pellet comprises a compositematerial comprising activated coal fines complexed to combustibletether-bearing anchor particles. In additional aspects, theenergy-bearing pellet comprises a composite material comprising anenergy-containing fine material and a combustible anchor particle in acomplex, the complex further comprising an interacting pair ofpolyelectrolytes, wherein the first of the pair of polyelectrolytes isbound to the energy-containing fine material and the second of the pairof polyelectrolytes is bound to the combustible anchor particle.

In some embodiments, the removable complex formed by a method of theinvention is removed by a process selected from the group consisting offiltration, centrifugation, skimming and gravitational settling.

In yet another embodiment, the invention is a system for removingparticulate matter from a fluid, comprising an activating materialcapable of being affixed to the particulate matter to form an activatedparticle; a tether-bearing anchor particle capable of attaching to theactivated particle to form a removable complex in the fluid; and aseparator for separating the removable complex from the fluid, therebyremoving the particulate matter; wherein the fluid is a waste tailingfluid derived from energy production or a mining process.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic showing the activated-tethered-anchored (ATA)system comprising three basic components: an activator polymer, a tetherpolymer and an anchor particle; the ATA system is contacted with theliquid fine tailing slurry resulting in self-assembly of the solidmaterial and the expulsion of water.

FIG. 2 is a reproduction of a photograph showing filtrates of and solidmaterial filtered from samples containing activated coal slurry treatedwith tethered filter cake (FC) and two samples of coal processed refuse(CPR1 and CPR2).

FIG. 3A shows a suspension of clay fines containing 5% by weight solids.

FIG. 3B shows the suspension of clay fines after adding an activatorpolymer.

FIG. 4 shows an 85% by weight sand slurry.

FIG. 5 shows the result of mixing an activated clay fines stream with aslurry containing tether-bearing sand anchor particles.

FIG. 6A shows the separation of the mixture in FIG. 5 by gravityfiltration.

FIG. 6B shows the filtered solids from the filtration shown in FIG. 6A.

FIG. 7 presents Graph 1 showing Solids Content (%) and Turbidity (NTU)as a function of tether dosage (ppm).

FIG. 8 presents Graph 2 showing Solids Content (%) and Turbidity (NTU)as a function of activator dosage (ppm).

DETAILED DESCRIPTION

Disclosed herein are systems and methods for removing finely dispersedmaterials or “fines” from wastewater streams produced during miningoperations. In embodiments, the clay fines produced during phosphatebeneficiation can be removed with these systems and methods. Inembodiments, other types of fines can be removed where thesecontaminants are suspended in aqueous solutions.

These systems and methods employ three subprocesses: (1) the“activation” of the wastewater stream bearing the fines by exposing itto a dose of a flocculating polymer that attaches to the fines; (2) thepreparation of “anchor particles,” fine particles such as sand bytreating them with a “tether” polymer that attaches to the anchorparticles; and (3) adding the tether-bearing anchor particles to theactivated wastewater stream containing the fines, so that thetether-bearing anchor particles form complexes with the activated fines.The activator polymer and the tether polymer have been selected so thatthey have a natural affinity with each other. Combining the activatedfines with the tether-bearing anchor particles rapidly forms a solidcomplex that can be separated from the suspension fluid with aseparator, resulting in a stable mass that can be easily and safelystored, along with clarified water that can be used for other industrialpurposes. As used herein, the term “separator” refers to any mechanism,device, or method that separates the solid complex from the suspensionfluid, i.e., that separates the removable complexes of tether-bearinganchor particle and activated particles from the fluid. Following theseparation process, the stable mass can be used for beneficial purposes,as can the clarified water. As an example, the clarified water could berecycled for use on-site in further processing and beneficiation ofores. As an example, the stable mass could be used for constructionpurposes at the mine operation (roads, walls, etc.), or could be used asa construction or landfill material offsite. Dewatering to separate thesolids from the suspension fluid can take place in seconds, relying onlyon gravity filtration.

Disclosed herein are systems and methods for enhancing the settlementrate of dispersed fine materials by incorporating them within a coarserparticulate matrix, so that solids can be removed from aqueoussuspension as a material having mechanical stability. The systems andmethods disclosed herein involve three components: activating the fineparticles, tethering them to anchor particles, and sedimenting the fineparticle-anchor particle complex.

Generally speaking, the fines in the wastewater stream are “activated”by exposure to a dosing of flocculating polymer. Separately, the sandparticles or other “anchor” particles are exposed to a polymer “tether.”The activator and tether are chosen so they have a natural affinitytowards each other. Combining the two streams, the activated fines withtether-bearing anchors, produces a stable solid that forms rapidly. Thesolid can be separated from the clarified water in which it resides by adewatering process, for example by gravity filtration, which can quicklyyield a mass that can be easily and safely stored.

1. Activation

As used herein, the term “activation” refers to the interaction of anactivating material, such as a polymer, with suspended particles in aliquid medium, such as an aqueous solution. In embodiments, highmolecular weight polymers can be introduced into the particulatedispersion, so that these polymers interact, or complex, with fineparticles. The polymer-particle complexes interact with other similarcomplexes, or with other particles, and form agglomerates.

This “activation” step can function as a pretreatment to prepare thesurface of the fine particles for further interactions in the subsequentphases of the disclosed system and methods. For example, the activationstep can prepare the surface of the fine particles to interact withother polymers that have been rationally designed to interact therewithin an optional, subsequent “tethering” step, as described below. Not tobe bound by theory, it is believed that when the fine particles arecoated by an activating material such as a polymer, these coatedmaterials can adopt some of the surface properties of the polymer orother coating. This altered surface character in itself can beadvantageous for sedimentation, consolidation and/or dewatering. Inanother embodiment, activation can be accomplished by chemicalmodification of the particles. For example, oxidants or bases/alkaliscan increase the negative surface energy of particulates, and acids candecrease the negative surface energy or even induce a positive surfaceenergy on suspended particulates. In another embodiment, electrochemicaloxidation or reduction processes can be used to affect the surfacecharge on the particles. These chemical modifications can produceactivated particulates that have a higher affinity for tethered anchorparticles as described below.

Particles suitable for modification, or activation, can include organicor inorganic particles, or mixtures thereof. Inorganic particles caninclude one or more materials such as calcium carbonate, dolomite,calcium sulfate, kaolin, talc, titanium dioxide, sand, diatomaceousearth, aluminum hydroxide, silica, other metal oxides and the like. Sandor other fine fractions of the solids, such as sand recovered from themining process itself, is preferred. Organic particles can include oneor more materials such as starch, modified starch, polymeric spheres(both solid and hollow), and the like. Particle sizes can range from afew nanometers to few hundred microns. In certain embodiments,macroscopic particles in the millimeter range may be suitable.

In embodiments, a particle, such as an amine-modified particle, maycomprise materials such as lignocellulosic material, cellulosicmaterial, vitreous material, cementitious material, carbonaceousmaterial, plastics, elastomeric materials, and the like. In embodiments,cellulosic and lignocellulosic materials may include wood materials suchas wood flakes, wood fibers, wood waste material, wood powder, lignins,or fibers from woody plants.

Examples of inorganic particles include clays such as attapulgite andbentonite. In embodiments, the inorganic compounds can be vitreousmaterials, such as ceramic particles, glass, fly ash and the like. Theparticles may be solid or may be partially or completely hollow. Forexample, glass or ceramic microspheres may be used as particles.Vitreous materials such as glass or ceramic may also be formed as fibersto be used as particles. Cementitious materials may include gypsum,Portland cement, blast furnace cement, alumina cement, silica cement,and the like. Carbonaceous materials may include carbon black, graphite,carbon fibers, carbon microparticles, and carbon nanoparticles, forexample carbon nanotubes.

In embodiments, the particle can be substantially larger than the fineparticulates it is separating out from the process stream. For example,for the removal of particulate matter with approximate diameters lessthan 50 microns, particles may be selected for modification havinglarger dimensions. In other embodiments, the particle can besubstantially smaller than the particulate matter it is separating outof the process stream, with a number of such particles interacting inorder to complex with the much larger particulate matter. Particles mayalso be selected for modification that have shapes adapted for easiersettling when compared to the target particulate matter: sphericalparticles, for example, may advantageously be used to remove flake-typeparticulate matter. In other embodiments, dense particles may beselected for modification, so that they settle rapidly when complexedwith the fine particulate matter in the process stream. In yet otherembodiments, extremely buoyant particles may be selected formodification, so that they rise to the fluid surface after complexingwith the fine particulate matter, allowing the complexes to be removedvia a skimming process rather than a settling-out process. Inembodiments where the modified particles are used to form a filter, asin a filter cake, the particles selected for modification can be chosenfor their low packing density or porosity. Advantageously, particles canbe selected that are indigenous to a particular geographical regionwhere the particulate removal process would take place. For example,sand can be advantageously used as the particle to be modified forremoving particulate matter from the waste stream of phosphate mining,because sand is a byproduct of phosphate beneficiation and is thereforefound abundantly at phosphate mining sites.

In embodiments, plastic materials may be used as particles. Boththermoset and thermoplastic resins may be used to form plasticparticles. Plastic particles may be shaped as solid bodies, hollowbodies or fibers, or any other suitable shape. Plastic particles can beformed from a variety of polymers. A polymer useful as a plasticparticle may be a homopolymer or a copolymer. Copolymers can includeblock copolymers, graft copolymers, and interpolymers. In embodiments,suitable plastics may include, for example, addition polymers (e.g.,polymers of ethylenically unsaturated monomers), polyesters,polyurethanes, aramid resins, acetal resins, formaldehyde resins, andthe like. Additional polymers can include, for example, polyolefins,polystyrene, and vinyl polymers. Polyolefins can include, inembodiments, polymers prepared from C₂-C₁₀ olefin monomers, e.g.,ethylene, propylene, butylene, dicyclopentadiene, and the like. Inembodiments, poly(vinyl chloride) polymers, acrylonitrile polymers, andthe like can be used. In embodiments, useful polymers for the formationof particles may be formed by condensation reaction of a polyhydriccompound (e.g., an alkylene glycol, a polyether alcohol, or the like)with one or more polycarboxylic acids. Polyethylene terephthalate is anexample of a suitable polyester resin. Polyurethane resins can includepolyether polyurethanes and polyester polyurethanes. Plastics may alsobe obtained for these uses from waste plastic, such as post-consumerwaste including plastic bags, containers, bottles made of high densitypolyethylene, polyethylene grocery store bags, and the like.

In embodiments, plastic particles can be formed as expandable polymericpellets. Such pellets may have any geometry useful for the specificapplication, whether spherical, cylindrical, ovoid, or irregular.Expandable pellets may be pre-expanded before using them. Pre-expansioncan take place by heating the pellets to a temperature above theirsoftening point until they deform and foam to produce a loosecomposition having a specific density and bulk. After pre-expansion, theparticles may be molded into a particular shape and size. For example,they may be heated with steam to cause them to fuse together into alightweight cellular material with a size and shape conforming to themold cavity. Expanded pellets may be 2-4 times larger than unexpandedpellets. As examples, expandable polymeric pellets may be formed frompolystyrenes and polyolefins. Expandable pellets are available in avariety of unexpanded particle sizes. Pellet sizes, measured along thepellet's longest axis, on a weight average basis, can range from about0.1 to 6 mm.

In embodiments, the expandable pellets may be formed by polymerizing thepellet material in an aqueous suspension in the presence of one or moreexpanding agents, or by adding the expanding agent to an aqueoussuspension of finely subdivided particles of the material. An expandingagent, also called a “blowing agent,” is a gas or liquid that does notdissolve the expandable polymer and which boils below the softeningpoint of the polymer. Blowing agents can include lower alkanes andhalogenated lower alkanes, e.g., propane, butane, pentane, cyclopentane,hexane, cyclohexane, dichlorodifluoromethane, andtrifluorochloromethane, and the like. Depending on the amount of blowingagent used and the technique for expansion, a range of expansioncapabilities exist for any specific unexpanded pellet system. Theexpansion capability relates to how much a pellet can expand when heatedto its expansion temperature. In embodiments, elastomeric materials canbe used as particles. Particles of natural or synthetic rubber can beused, for example.

In embodiments, the particle can be substantially larger than the fineparticulates it is separating out from the process stream. For example,for the removal of particulate matter with approximate diameters lessthan 50 microns, particles may be selected for modification havinglarger dimensions. In other embodiments, the particle can besubstantially smaller than the particulate matter it is separating outof the process stream, with a number of such particles interacting inorder to complex with the much larger particulate matter. Particles mayalso be selected for modification that have shapes adapted for easiersettling when compared to the target particulate matter: sphericalparticles, for example, may advantageously be used to remove flake-typeparticulate matter. In other embodiments, dense particles may beselected for modification, so that they settle rapidly when complexedwith the fine particulate matter in the process stream. In yet otherembodiments, extremely buoyant particles may be selected formodification, so that they rise to the fluid surface after complexingwith the fine particulate matter, allowing the complexes to be removedvia a skimming process rather than a settling-out process. Inembodiments where the modified particles are used to form a filter, asin a filter cake, the particles selected for modification can be chosenfor their low packing density or porosity. Advantageously, particles canbe selected that are indigenous to a particular geographical regionwhere the particulate removal process would take place. For example,sand can be used as the particle to be modified for removing particulatematter from the waste stream (tailings) in phosphate mining or othermining activities.

It is envisioned that the complexes formed from the modified particlesand the particulate matter can be recovered and used for otherapplications. For example, when sand is used as the modified particleand it captures fine clay in tailings, the sand/clay combination can beused for road construction in the vicinity of the mining sites, due tothe less compactable nature of the complexes compared to other locallyavailable materials.

The “activation” step may be performed using flocculants or otherpolymeric substances. Preferably, the polymers or flocculants can becharged, including anionic or cationic polymers. In embodiments, anionicpolymers can be used, including, for example, olefinic polymers, such aspolymers made from polyacrylate, polymethacrylate, partially hydrolyzedpolyacrylamide, and salts, esters and copolymers thereof (such as(sodium acrylate/acrylamide) copolymers)polyacrylic acid,polymethacrylic acid, sulfonated polymers, such as sulfonatedpolystyrene, and salts, esters and copolymers thereof, and the like.Suitable polycations include: polyvinylamines, polyallylamines,polydiallyldimethylammoniums (e.g., thepolydiallyldimethylammoniumchloride, branched or linear polyethyleneimine, crosslinked amines(including epichlorohydrin/dimethylamine, andepichlorohydrin/alkylenediamines), quaternary ammonium substitutedpolymers, such as (acrylamide/dimethylaminoethylacrylate methyl chloridequat) copolymers and trimethylammoniummethylene-substituted polystyrene,polyvinylamine, and the like. Nonionic polymers suitable for hydrogenbonding interactions can include polyethylene oxide, polypropyleneoxide, polyhydroxyethylacrylate, polyhydroxyethylmethacrylate, and thelike. In embodiments, an activator such as polyethylene oxide can beused as an activator with a cationic tethering material in accordancewith the description of tethering materials below. In embodiments,activator polymers with hydrophobic modifications can be used.Flocculants such as those sold under the trademark MAGNAFLOC® by CibaSpecialty Chemicals can be used.

In embodiments, activators such as polymers or copolymers containingcarboxylate, sulfonate, phosphonate, or hydroxamate groups can be used.These groups can be incorporated in the polymer as manufactured;alternatively they can be produced by neutralization of thecorresponding acid groups, or generated by hydrolysis of a precursorsuch as an ester, amide, anhydride, or nitrile group. The neutralizationor hydrolysis step could be done on site prior to the point of use, orit could occur in situ in the process stream.

The activated particle can also be an amine functionalized or modifiedparticle. As used herein, the term “modified particle” can include anyparticle that has been modified by the attachment of one or more aminefunctional groups as described herein. The functional group on thesurface of the particle can be from modification using a multifunctionalcoupling agent or a polymer. The multifunctional coupling agent can bean amino silane coupling agent as an example. These molecules can bondto a particle surface (e.g., metal oxide surface) and then present theiramine group for interaction with the particulate matter. In the case ofa polymer, the polymer on the surface of the particles can be covalentlybound to the surface or interact with the surface of the particle and/orfiber using any number of other forces such as electrostatic,hydrophobic, or hydrogen bonding interactions. In the case that thepolymer is covalently bound to the surface, a multifunctional couplingagent can be used such as a silane coupling agent. Suitable couplingagents include isocyano silanes and epoxy silanes as examples. Apolyamine can then react with an isocyano silane or epoxy silane forexample. Polyamines include polyallyl amine, polyvinyl amine, chitosan,and polyethylenimine.

In embodiments, polyamines (polymers containing primary, secondary,tertiary, and/or quaternary amines) can also self-assemble onto thesurface of the particles or fibers to functionalize them without theneed of a coupling agent. For example, polyamines can self-assemble ontothe surface of the particles through electrostatic interactions. Theycan also be precipitated onto the surface in the case of chitosan forexample. Since chitosan is soluble in acidic aqueous conditions, it canbe precipitated onto the surface of particles by suspending theparticles in a chitosan solution and then raising the solution pH.

In embodiments, the amines or a majority of amines are charged. Somepolyamines, such as quaternary amines are fully charged regardless ofthe pH. Other amines can be charged or uncharged depending on theenvironment. The polyamines can be charged after addition onto theparticles by treating them with an acid solution to protonate theamines. In embodiments, the acid solution can be non-aqueous to preventthe polyamine from going back into solution in the case where it is notcovalently attached to the particle.

The polymers and particles can complex via forming one or more ionicbonds, covalent bonds, hydrogen bonding and combinations thereof, forexample. Ionic complexing is preferred.

To obtain activated fine materials, the activator could be introducedinto a liquid medium through several different means. For example, alarge mixing tank could be used to mix an activating material withtailings from mining operations that contain fine particulate materials.Alternatively, the activating material can be added along a transportpipeline and mixed, for example, by a static mixer or series of baffles.Activated particles are produced that can be treated with one or moresubsequent steps of tethering and anchor-separation.

The particles that can be activated are generally fine particles thatare resistant to sedimentation. Examples of particles that can befiltered in accordance with the invention include metals, sand,inorganic, or organic particles. The particles are generally fineparticles, such as particles having a mass mean diameter of less than 50microns or particle fraction that remains with the filtrate following afiltration with, for example, a 325 mesh filter. The particles to beremoved in the processes described herein are also referred to as“fines.”

2. Tethering

As used herein, the term “tethering” refers to an interaction between anactivated fine particle and an anchor particle (for example, asdescribed below). The anchor particle can be treated or coated with atethering material. The tethering material, such as a polymer, forms acomplex or coating on the surface of the anchor particles such that thetethered anchor particles have an affinity for the activated fines. Inembodiments, the selection of tether and activator materials is intendedto make the two solids streams complementary so that the activated fineparticles become tethered, linked or otherwise attached to the anchorparticle. When attached to activated fine particles via tethering, theanchor particles enhance the rate and completeness of sedimentation orremoval of the fine particles from the fluid stream.

In accordance with these systems and methods, the tethering materialacts as a complexing agent to affix the activated particles to an anchormaterial. In embodiments, sand can be used as an anchor material, as maya number of other substances, as set forth in more detail below. Inembodiments, a tethering material can be any type of material thatinteracts strongly with the activating material and that is connectableto an anchor particle.

As used herein, the term “anchor particle” refers to a particle thatfacilitates the separation of fine particles. Generally, anchorparticles have a density that is greater than the liquid process stream.For example, anchor particles that have a density of greater than 1.3g/cc can be used. Additionally or alternatively, the density of theanchor particles can be greater than the density of the fine particlesor activated particles. Alternatively, the density is less than thedispersal medium, or density of the liquid or aqueous stream.Alternatively, the anchor particles are simply larger than the fineparticles being removed. In embodiments, the anchor particles are chosenso that, after complexing with the fine particulate matter, theresulting complexes can be removed via a skimming process rather than asettling-out process, or they can be readily filtered out or otherwiseskimmed off. In embodiments, the anchor particles can be chosen fortheir low packing density or potential for developing porosity. Adifference in density or particle size can facilitate separating thesolids from the medium.

For example, for the removal of particulate matter with an approximatemass mean diameter less than 50 microns, anchor particles may beselected having larger dimensions, e.g., a mass mean diameter of greaterthan 70 microns. An anchor particle for a given system can have a shapeadapted for easier settling when compared to the target particulatematter: spherical particles, for example, may advantageously be used asanchor particles to remove particles with a flake or needle morphology.In other embodiments, increasing the density of the anchor particles maylead to more rapid settlement. Alternatively, less dense anchors mayprovide a means to float the fine particles, using a process to skim thesurface for removal. In this embodiment, one may choose anchor particleshaving a density of less than about 0.9 g/cc, for example, 0.5 g/cc, toremove fine particles from an aqueous process stream.

Advantageously, anchor particles can be selected that are indigenous toa particular geographical region where the particulate removal processwould take place. For example, sand can be used as the anchor particlefor use in removing fine particulate matter from the waste stream(tailings) of phosphate mining.

Suitable anchor particles can be formed from organic or inorganicmaterials, or any mixture thereof. Particles suitable for use as anchorparticles can include organic or inorganic particles, or mixturesthereof. In referring to an anchor particle, it is understood that sucha particle can be made from a single substance or can be made from acomposite. For example, coal can be used as an anchor particle incombination with another organic or inorganic anchor particle. Anycombination of inorganic or organic anchor particles can be used. Anchorparticle combinations can be introduced as mixtures of heterogeneousmaterials. Anchor particles can be prepared as agglomerations ofheterogeneous materials, or other physical combinations thereof. Forexample, an anchor particle can be formed from a particle of one type ofbiomass combined with a particle of another type of biomass. In anotherexample, an anchor particle can be formed from a combustible organicparticle complexed, coated or otherwise admixed with other organic orinorganic anchor particle materials. As an example, a combustibleorganic material can be combined with particles of ungelatinized starch.In embodiments, the starch can be gelatinized during a thermal dryingstep, optionally with the use of an alkali, to cause binding andstrengthening of the composite fuel product.

In embodiments, the organic material selected as an anchor particle canbe a coal particle, for example coal derived from coal mining orprocessing. As an example, coal that is collected as filter cake (FC)coal can be used as anchor particles. This technology has the advantageof using materials that are readily available on-site during coalprocessing to treat the fines being produced there. Anchor particles canbe energy-bearing (e.g., combustible) or non-energy-bearing (e.g.,minerals), or combinations thereof.

In accordance with these systems and methods, inorganic anchor particlescan include one or more materials such as calcium carbonate, dolomite,calcium sulfate, kaolin, talc, titanium dioxide, sand, diatomaceousearth, aluminum hydroxide, silica, other metal oxides and the like. Inembodiments, the coarse fraction of the solids recovered from the miningprocess itself can be used for anchor particles, for example, coal fromcoal mining. Organic particles can include one or more materials such asbiomass, starch, modified starch, polymeric spheres (both solid andhollow), and the like. Particle sizes can range from a few nanometers tofew hundred microns. In certain embodiments, macroscopic particles inthe millimeter range may be suitable.

In embodiments, a particle, such as an amine-modified particle, cancomprise materials such as lignocellulosic material, cellulosicmaterial, minerals, vitreous material, cementitious material,carbonaceous material, plastics, elastomeric materials, and the like. Inembodiments, cellulosic and lignocellulosic materials may include woodmaterials such as wood flakes, wood fibers, wood waste material, woodpowder, lignins, or fibers from woody plants. Organic materials caninclude various forms of organic waste, including biomass and includingparticulate matter from post-consumer waste items such as old tires andcarpeting materials.

Examples of inorganic particles include clays such as attapulgite andbentonite. In embodiments, the inorganic compounds can be vitreousmaterials, such as ceramic particles, glass, fly ash and the like. Theparticles may be solid or may be partially or completely hollow. Forexample, glass or ceramic microspheres may be used as particles.Vitreous materials such as glass or ceramic may also be formed as fibersto be used as particles. Cementitious materials may include gypsum,Portland cement, blast furnace cement, alumina cement, silica cement,and the like. Carbonaceous materials may include carbon black, graphite,carbon fibers, carbon microparticles, and carbon nanoparticles, forexample carbon nanotubes.

In other embodiments, the inorganic material selected as an anchorparticle can be produced during coal preparation and processing, asdescribed above. For example, the inorganic material used as an anchorparticle can be derived from the mineral waste products of coalprocessing, e.g., coal processing refuse (CPR). Other inorganicmaterials available on-site (sand, etc.) can be used as anchorparticles, either alone or in combination with other inorganic ororganic anchor particles. This technology has the advantage of usingmaterials that are readily available on-site during coal processing totreat the fines being produced there.

In embodiments, plastic materials may be used as particles. Boththermoset and thermoplastic resins may be used to form plasticparticles. Plastic particles may be shaped as solid bodies, hollowbodies or fibers, or any other suitable shape. Plastic particles can beformed from a variety of polymers. A polymer useful as a plasticparticle may be a homopolymer or a copolymer. Copolymers can includeblock copolymers, graft copolymers, and interpolymers. In embodiments,suitable plastics may include, for example, addition polymers (e.g.,polymers of ethylenically unsaturated monomers), polyesters,polyurethanes, aramid resins, acetal resins, formaldehyde resins, andthe like. Addition polymers can include, for example, polyolefins,polystyrene, and vinyl polymers. Polyolefins can include, inembodiments, polymers prepared from C₂-C₁₀ olefin monomers, e.g.,ethylene, propylene, butylene, dicyclopentadiene, and the like. Inembodiments, poly(vinyl chloride) polymers, acrylonitrile polymers, andthe like can be used. In embodiments, useful polymers for the formationof particles may be formed by condensation reaction of a polyhydriccompound (e.g., an alkylene glycol, a polyether alcohol, or the like)with one or more polycarboxylic acids. Polyethylene terephthalate is anexample of a suitable polyester resin. Polyurethane resins can includepolyether polyurethanes and polyester polyurethanes. Plastics may alsobe obtained for these uses from waste plastic, such as post-consumerwaste including plastic bags, containers, bottles made of high densitypolyethylene, polyethylene grocery store bags, and the like. Inembodiments, elastomeric materials can be used as particles. Particlesof natural or synthetic rubber can be used, for example.

Advantageously, anchor particles can be selected from biomass, so thatthey complex with the fines to form a biomass-fines composite solid.This process can be advantageous in producing a combustible complex, forexample by complexing coal fines with a biomass tether. Biomass can bederived from vegetable sources or animal sources. Biomass can be derivedfrom waste materials, including post-consumer waste, animal or vegetablewaste, agricultural waste, sewage, and the like. In embodiments, thebiomass sourced materials are to be processed so that they formparticles of an appropriate size for tethering and combining with theactivated fines. Particle sizes of, e.g., 0.01-50 millimeters aredesirable. Processing methods can include grinding, milling, pumping,shearing, and the like. For example, hammer mills, ball mills, and rodmills can be used to reduce oversized materials to an appropriate size.In embodiments, additives might be used in the processing of the anchorparticles to improve efficiency, reduce energy requirements, or increaseyield. These processing additives include polymers, surfactants, andchemicals that enhance digestion or disintegration. Optionally, othertreatment modalities, such as exposure to cryogenic liquids (e.g.,liquid nitrogen or solid carbon dioxide) can be employed to facilitateforming anchor particles of appropriate size from biomass. It isunderstood that biomass-derived anchor particles can be formed asparticles of any morphology (regular or irregular, plate-shaped, flakes,cylindrical, spherical, needle-like, etc.) or can be formed as fibers.Fibrous materials may be advantageous in that they facilitatedewatering/filtration of the composite material being formed by thesesystems and methods, and they can add strength to such compositematerials.

Vegetable sources of biomass can include fibrous material, particulatematerial, amorphous material, or any other material of vegetable origin.Vegetable sources can be predominately cellulosic, e.g., derived fromcotton, jute, flax, hemp, sisal, ramie, and the like. Vegetable sourcescan be derived from seeds or seed cases, such as cotton or kapok, orfrom nuts or nutshells, including without limitation, peanut shells,walnut shells, coconut shells, and the like. Vegetable sources caninclude the waste materials from agriculture, such as corn stalks,stalks from grain, hay, straw, or sugar cane (e.g., bagasse). Vegetablesources can include leaves, such as sisal, agave, deciduous leaves fromtrees, shrubs and the like, leaves or needles from coniferous plants,and leaves from grasses. Vegetable sources can include fibers derivedfrom the skin or bast surrounding the stem of a plant, such as flax,jute, kenaf, hemp, ramie, rattan, soybean husks, corn husks, rice hulls,vines or banana plants. Vegetable sources can include fruits of plantsor seeds, such as coconuts, peach pits, olive pits, mango seeds,corncobs or corncob byproducts (“bees wings”) and the like. Vegetablesources can include the stalks or stems of a plant, such as wheat, rice,barley, bamboo, and grasses. Vegetable sources can include wood, woodprocessing products such as sawdust, and wood, and wood byproducts suchas lignin.

Animal sources of biomass can include materials from any part of avertebrate or invertebrate animal, fish, bird, or insect. Such materialstypically comprise proteins, e.g., animal fur, animal hair, animalhoofs, and the like. Animal sources can include any part of the animal'sbody, as might be produced as a waste product from animal husbandry,farming, meat production, fish production or the like, e.g., catgut,sinew, hoofs, cartilaginous products, etc. Animal sources can includethe dried saliva or other excretions of insects or their cocoons, e.g.,silk obtained from silkworm cocoons or spider's silk. Animal sources caninclude dairy byproducts such as whey, whey permeate solids, milksolids, and the like. Animal sources can be derived from feathers ofbirds or scales of fish.

In embodiments, the anchor particle can be substantially larger than thefine particulates it is separating out from the process stream. Forexample, for the removal of fines with approximate diameters less than50 microns, anchor particles may be selected for modification havinglarger dimensions. In other embodiments, the particle can besubstantially smaller than the particulate matter it is separating outof the process stream, with a number of such particles interacting inorder to complex with the much larger particulate matter. Particles mayalso be selected for modification that have shapes adapted for easiersettling when compared to the target particulate matter: sphericalparticles, for example, may advantageously be used to remove flake-typeparticulate matter. In other embodiments, dense particles may beselected for modification, so that they settle rapidly when complexedwith the fine particulate matter in the process stream. In yet otherembodiments, extremely buoyant particles may be selected formodification, so that they rise to the fluid surface after complexingwith the fine particulate matter, allowing the complexes to be removedvia a skimming process rather than a settling-out process. Inembodiments where the modified particles are used to form a filter, asin a filter cake, the particles selected for modification can be chosenfor their low packing density or porosity. Advantageously, particles canbe selected that are indigenous to a particular geographical regionwhere the particulate removal process would take place. For example,sand can be used as the particle to be modified for removing particulatematter from the waste stream (tailings) in phosphate mining or othermining activities.

It is envisioned that the complexes formed from the modified particlesand the particulate matter can be recovered and used for otherapplications. For example, when sand is used as the modified particleand it captures fine clay in tailings, the sand/clay combination can beused for road construction in the vicinity of the mining sites, due tothe less compactable nature of the complexes compared to other locallyavailable materials.

Anchor particle sizes (as measured as a mean diameter) can have a sizeup to few hundred microns, preferably greater than about 70 microns. Incertain embodiments, macroscopic anchor particles up to and greater thanabout 1 mm may be suitable. Recycled materials or waste, particularlyrecycled materials and waste having a mechanical strength and durabilitysuitable to produce a product useful in building roads and the like, or(in other embodiments) capable of combustion, are particularlyadvantageous.

As an example of a tethering material used with an anchor particle inaccordance with these systems and methods, chitosan can be precipitatedonto sand particles, for example, via pH-switching behavior. Thechitosan can have affinity for anionic systems that have been used toactivate fine particles. Anchor particles can be complexed withtethering agents, such agents being selected so that they interact withthe polymers used to activate the coal fines. In one example, partiallyhydrolyzed polyacrylamide polymers can be used to activate particles,resulting in a particle with anionic charge properties. The cationiccharge of the chitosan will attract the anionic charge of the activatedparticles, to attach the sand particles to the activated fine particles.

In embodiments, various interactions such as electrostatic, hydrogenbonding or hydrophobic behavior can be used to affix an activatedparticle or particle complex to a tethering material complexed with ananchor particle.

In embodiments, the anchor particles can be combined with a polycationicpolymer, for example a polyamine. One or more populations of anchorparticles may be used, each being activated with a tethering agentselected for its attraction to the activated coal fines and/or to theother anchor particle's tether. The tethering functional group on thesurface of the anchor particle can be from modification using amultifunctional coupling agent or a polymer. The multifunctionalcoupling agent can be an amino silane coupling agent as an example.These molecules can bond to an anchor particle's surface and thenpresent their amine group for interaction with the activated coal fines.In the case of a tethering polymer, the polymer on the surface of theparticles can be covalently bound to the surface or interact with thesurface of the anchor particle and/or fiber using any number of otherforces such as electrostatic, hydrophobic, or hydrogen bondinginteractions. In the case that the polymer is covalently bound to thesurface, a multifunctional coupling agent can be used such as a silanecoupling agent. Suitable coupling agents include isocyano silanes andepoxy silanes as examples. A polyamine can then react with an isocyanosilane or epoxy silane for example. Polyamines include polyallyl amine,polyvinyl amine, chitosan, and polyethylenimine.

In embodiments, polyamines (polymers containing primary, secondary,tertiary, and/or quaternary amines) can also self-assemble onto thesurface of the particles or fibers to functionalize them without theneed of a coupling agent. For example, polyamines can self-assemble ontothe surface of the particles through electrostatic interactions. Theycan also be precipitated onto the surface in the case of chitosan forexample. Since chitosan is soluble in acidic aqueous conditions, it canbe precipitated onto the surface of particles by suspending theparticles in a chitosan solution and then raising the solution pH.

In embodiments, the amines or a majority of amines are charged. Somepolyamines, such as quaternary amines are fully charged regardless ofthe pH. Other amines can be charged or uncharged depending on theenvironment. The polyamines can be charged after addition onto theparticles by treating them with an acid solution to protonate theamines. In embodiments, the acid solution can be non-aqueous to preventthe polyamine from going back into solution in the case where it is notcovalently attached to the particle.

The polymers and particles can complex via forming one or more ionicbonds, covalent bonds, hydrogen bonding and combinations thereof, forexample. Ionic complexing is preferred.

As an example of a tethering material used with an anchor particle inaccordance with these systems and methods, chitosan can be precipitatedonto anchor particles, for example, via pH-switching behavior. Thechitosan as a tether can have affinity for anionic systems that havebeen used to activate fine particles. In one example, partiallyhydrolyzed polyacrylamide polymers can be used to activate coal fines,resulting in a particle with anionic charge properties. The cationiccharge of the chitosan will attract the anionic charge of the activatedparticles, to attach the anchor particles to the activated coal fines.In the foregoing example, electrostatic interactions can govern theassembly of the activated fine particle complexes bearing the anionicpartially-hydrolyzed polyacrylamide polymer and the cationic anchorparticles complexed with the chitosan tethering material.

In embodiments, polymers such as linear or branched polyethyleneiminecan be used as tethering materials. It would be understood that otheranionic or cationic polymers could be used as tethering agents, forexample polydiallyldimethylammonium chloride (poly(DADMAC)). In otherembodiments, cationic tethering agents such as epichlorohydrindimethylamine (epi/DMA), styrene maleic anhydride imide (SMAI),polyethylene imide (PEI), polyvinylamine, polyallylamine, amine-aldehydecondensates, poly(dimethylaminoethyl acrylate methyl chloridequaternary) polymers and the like can be used. Advantageously, cationicpolymers useful as tethering agents can include quaternary ammonium orphosphonium groups. Advantageously, polymers with quaternary ammoniumgroups such as poly(DADMAC) or epi/DMA can be used as tethering agents.In other embodiments, polyvalent metal salts (e.g., calcium, magnesium,aluminum, iron salts, and the like) can be used as tethering agents. Inother embodiments cationic surfactants such asdimethyldialkyl(C8-C22)ammonium halides, alkyl(C8-C22)trimethylammoniumhalides, alkyl(C8-C22)dimethylbenzylammonium halides, cetyl pyridiniumchloride, fatty amines, protonated or quaternized fatty amines, fattyamides and alkyl phosphonium compounds can be used as tethering agents.In embodiments, polymers having hydrophobic modifications can be used astethering agents.

The efficacy of a tethering material, however, can depend on theactivating material. A high affinity between the tethering material andthe activating material can lead to a strong and/or rapid interactionthere between. A suitable choice for tether material is one that canremain bound to the anchor surface, but can impart surface propertiesthat are beneficial to a strong complex formation with the activatorpolymer. For example, a polyanionic activator can be matched with apolycationic tether material or a polycationic activator can be matchedwith a polyanionic tether material. In one embodiment, a poly(sodiumacrylate-co-acrylamide) activator is matched with a chitosan tethermaterial.

In hydrogen bonding terms, a hydrogen bond donor should be used inconjunction with a hydrogen bond acceptor. In embodiments, the tethermaterial can be complementary to the chosen activator, and bothmaterials can possess a strong affinity to their respective depositionsurfaces while retaining this surface property.

In other embodiments, cationic-anionic interactions can be arrangedbetween activated coal fines and tether-bearing anchor particles. Theactivator may be a cationic or an anionic material, as long as it has anaffinity for the fine particles to which it attaches. The complementarytethering material can be selected to have affinity for the specificanchor particles being used in the system. In other embodiments,hydrophobic interactions can be employed in the activation-tetheringsystem.

It is envisioned that the complexes formed from the tether-bearinganchor particles and the activated coal fines can be recovered and usedfor other applications. For example, the complexes can be rapidlyseparated from water and can be recovered for compaction into coalpellets to be used for combustion. When a combustible anchor particle isselected, the entire coal-anchor complex can be used for energyproduction. Other anchor particles can be selected to form specializedcomposites with the activated coal fines, as disclosed below in moredetail.

Advantageously, anchor particles can be selected that are indigenous toa particular geographical region where the particulate removal processwould take place. For example, sand can be used as the particle to bemodified for removing particulate matter from the waste stream(tailings) in phosphate mining or other mining activities.

Suitable anchor particles can be formed from organic or inorganicmaterials, or any mixture thereof. Anchor particle sizes (as measured asa mass mean diameter) can have a size up to few hundred microns,preferably greater than about 70 microns. In certain embodiments,macroscopic anchor particles up to and greater than about 1 mm may besuitable. Recycled materials or waste, particularly recycled materialsand waste having a mechanical strength and durability suitable toproduce a product useful in building roads and the like are particularlyadvantageous.

As an example of a tethering material used with an anchor particle inaccordance with these systems and methods, chitosan can be precipitatedonto sand particles, for example, via pH-switching behavior. Thechitosan can have affinity for anionic systems that have been used toactivate fine particles. In one example, partially hydrolyzedpolyacrylamide polymers can be used to activate particles, resulting ina particle with anionic charge properties. The cationic charge of thechitosans will attract the anionic charge of the activated particles, toattach the sand particles to the activated fine particles.

In embodiments, various interactions such as electrostatic, hydrogenbonding or hydrophobic behavior can be used to affix an activatedparticle or particle complex to a tethering material complexed with ananchor particle. In the foregoing example, electrostatic interactionscan govern the assembly of the activated fine particle complexes bearingthe anionic partially-hydrolyzed polyacrylamide polymer and the cationicsand particles complexed with the chitosan tethering material.

In embodiments, polymers such as linear or branched polyethyleneiminecan be used as tethering materials. It would be understood that otheranionic or cationic polymers could be used as tethering agents, forexample polydiallyldimethylammonium chloride. The efficacy of atethering material, however, can depend on the activating material. Ahigh affinity between the tethering material and the activating materialcan lead to a strong and/or rapid interaction there between.

A suitable choice for tether material is one that can remain bound tothe anchor surface, but can impart surface properties that arebeneficial to a strong complex formation with the activator polymer. Forexample, a polyanionic activator can be matched with a polycationictether material or a polycationic activator can be matched with apolyanionic tether material. In hydrogen bonding terms, a hydrogen bonddonor should be used in conjunction with a hydrogen bond acceptor. Inembodiments, the tether material can be complimentary to the chosenactivator, and both materials can possess a strong affinity to theirrespective deposition surfaces while retaining this surface property.

In other embodiments, cationic-anionic interactions can be arrangedbetween activated fine particles and tether-bearing anchor particles.The activator may be a cationic or an anionic material, as long as ithas an affinity for the fine particles to which it attaches. Thecomplementary tethering material can be selected to have affinity forthe specific anchor particles being used in the system. In otherembodiments, hydrophobic interactions can be employed in theactivation-tethering system.

The anchor particle material is preferably added in an amount thatpermits a flowable slurry. For example, the particle material can beadded in an amount greater than 1 gram/liter but less than the amountwhich results in a non-flowable sludge, amounts between about 1 to about10 grams/liter, preferably 2 to 6 g/l are often suitable. In someembodiments, it may be desirable to maintain the concentration of theanchor particles to 20 g/l or higher. The anchor particles may be fresh(unused) material, recycled, cleaned ballast, or recycled, uncleanedballast.

In embodiments, for example when sand is chosen as an anchor particle,higher amounts of the particle material may be added. For example, sandcan be added in a range between 1-300 gm/l, preferably between 50-300gm/l, for example at a dosage level of 240 gm/l.

3. Removal of the Anchor-Tether-Activator Complexes

It is envisioned that the complexes formed from the anchor particles andthe activated particulate matter can be recovered and used for otherapplications. For example, when sand is used as the modified particleand it captures fine clay in tailings, the dewatered sand/claycombination can be used for road construction in the vicinity of themining sites, due to the less compactable nature of the complexescompared to other locally available materials. As another example, asand/clay complex could be used to fill in strip mining pits, such aswould be found at phosphate mining operations. In other embodiments,complexes with anchor particles and fines could be used in a similarmanner on-site to fill in abandoned mines, or the complexes could beused off-site for landfill or construction purposes. The uses of thesolid material produced by the systems and methods disclosed herein willvary depending on the specific constituents of the material.

In embodiments, the interactions between the activated fine particlesand the tether-bearing anchor particles can enhance the mechanicalproperties of the complex that they form. For example, an activated fineparticle or collection thereof can be durably bound to one or moretether-bearing anchor particles, so that they do not segregate or movefrom the position that they take on the particles. This property of thecomplex can make it mechanically more stable.

Increased compatibility of the activated fine materials with a denser(anchor) matrix modified with the appropriate tether polymer can lead tofurther mechanical stability of the resulting composite material. Thisbecomes quite important when dealing with tailings resulting frommining. This composite material can then be further utilized within theproject for road building, dyke construction, or even land reclamation,rather than simply left in a pond to settle at a much slower rate.

A variety of techniques are available for removing theactivated-tethered-anchored (ATA) complexes from the fluid stream. Forexample, the tether-bearing anchor particles can be mixed into a streamcarrying activated fine particles, and the complexes can then beseparated via a settling process such as gravity or centrifugation. Inanother method, the process stream carrying the activated fine particlescould flow through a bed or filter cake of the tether-bearing anchorparticles. In any of these methods, the modified particles interact withthe fine particulates and pull them out of suspension so that laterseparation removes both modified particles and fine particulates.

As would be appreciated by artisans of ordinary skill, a variety ofseparation processes could be used to remove the complexes of modifiedparticles and fine particulates. In the aforesaid removal processes,mechanical interventions for separating the ATA complexes can beintroduced, employing various devices as separators (filters, skimmers,centrifuges, and the like). Or other separation techniques can beemployed. For example, if the anchor particles had magnetic properties,the complexes formed by the interaction of tether-bearing anchorparticles and activated fine particulates could be separated using amagnetic field. As another example, if the tether-bearing anchorparticles were prepared so that they were electrically conductive, thecomplexes formed by the interaction of tether-bearing anchor particlesand activated fine particulates could be separated using an electricfield. As would be further appreciated by those of ordinary skill,tether-bearing anchor particles could be designed to complex with aspecific type of activated particulate matter. The systems and methodsdisclosed herein could be used for complexing with organic wasteparticles, for example. Other activation-tethering-anchoring systems maybe envisioned for removal of suspended particulate matter in fluidstreams, including gaseous streams.

4. Specialized Composites

Composites can be formed with coal fines by selecting anchor particleshaving particular properties. For example, selecting a combustibleanchor particle allows the coal-particle complex to be used for energyproduction. As another example, selecting an ungelatinized starchparticle as an anchor particle allows the formation of a coal-particlecomplex that can be formed into an energy-bearing pellet that respondsto heating by expanding and becoming porous, facilitating rapid andefficient combustion.

In an embodiment, a fine powdered uncooked starch, e.g., ungelatinized,can be selected as anchor particles. A complementary pair of activatorand tethering agents can be selected, whereby the starch particles canbe coated with the tether agent and the coal fines can be coated withthe activator. As an example, a polyelectrolyte pair including apolyanionic polymer and a polycationic polymer can be selected. Thepolyelectrolyte pair is selected to exhibit strong attraction to eachother, even when surrounded with water molecules and other dissolvedions. Polyelectrolytes can be selected that are capable of spontaneousself-assembly on coal fines and starch particles, respectively, todeposit a monolayer or near-monolayer film on the fines and theparticles.

In these embodiments, the tethering agent is disposed upon the starchparticles to form a tether-bearing anchor. The activator is added to thecoal fines. The two fluid streams can then be mixed together, wherebythe charge-charge attraction complexes the tether-bearing anchorparticles with the activated coal fines, expelling intervening watermolecules and precipitating macroscopic coal-starch aggregates.

In embodiments, polyanions including carboxymethyl cellulose (CMC),carboxymethyl starch (CMS), pectin, xanthan gum, alginate, polyacrylicacid, polymethacrylic acid, hydrolyzed polyacrylamide, styrene maleicanhydride copolymer, certain proteins and peptides rich in amino acidscontaining carboxylic acid side groups, and the like, can be used in thesystem. In embodiments, polycations including polyethyleneimine,chitosan, polyvinylamine, polyallylamine, polydimethyldiallylammoniumchloride (PDAC), epi-dimethylamine (epi-DMA), and certain proteins andpeptides rich in amino acids with side amino groups, and the like, canbe used in the system. Other polyanion-polycation pairs, including thosedisclosed above, will be apparent to those of ordinary skill in the art.

In an embodiment, the coal fine slurry can be treated with one type ofpolyelectrolyte while a starch powder is lightly wetted with another(e.g., sprayed with or a concentrated dispersion of the starch powder isadded to a dilute polyelectrolyte solution). The charged starch is thenmixed with the coal slurry containing pre-coated coal fines covered withcounter-charged polyelectrolyte. Since both solids have an ultrathinpolymer layer on their surface, the strong charge-charge attractionimmediately brings the disparate particles together, causing firmaggregation and precipitating cohesive pellets. Depending on theintensity of stirring, pellets of different but controlled size readilyform. The consolidated aggregates can be easily recovered by passing thecombined liquid stream over a coarse wire mesh. Clarified water devoidof either fine powder exits the system, posing little environmentalconcern. Mechanical pressure or vacuum can be applied to further dewaterthe solids. Since water is largely excluded from the interior of thepellets, little drying by heat is needed. In arid or semi-arid areas,pellets can dry rapidly at room temperature. Other adjuncts to thepellet formation process, such as adding starches and other pelletizingingredients, are consistent with these systems and methods, as would beunderstood by those of ordinary skill in the art. In embodiments,additives to improve dewatering of the solids can be introduced usinghydrophobic materials and practices known in the art.

In embodiments, the complexes formed from theungelatinized-starch-coal-fines composite can be shaped intoenergy-bearing pellets that possess a unique performance feature: uponmodest heating, the starch greatly expands (foams) leaving numerousinterior channels for oxygen permeation. This rapid expansion can causethe pellets to disintegrate upon aggressive heating. Not to be bound bytheory, it is understood that the thermal decomposition of theoxygen-rich sugar building blocks of starch can create oxygen radicalsthat can speed up combustion of nearby coal particles (which aretypically difficult to burn due to their high aromaticity).

Other difficult-to-burn energy-containing particles can be similarlytreated by the foregoing systems and methods so that they can be burnedmore efficiently. Solutions bearing such energy-containing materials(e.g., coke from coking of heavy crude or bitumen, lignin from pulping,shredded or pulverized recycled plastics/rubbers, fatty acids and wasteoils/shortenings that are semi-solid-like) can be treated with activatorpolymers and complexed with tether-bearing anchor particles, e.g.,starch particles as described above. Other tether-bearing anchorparticles can be used to complex with the activated energy-containingmaterial, such anchor particles being selected to enhance the combustionprocess or to effect other desirable chemical reactions. Alternatively,the energy-containing particles can be used as anchor particles, to becombined with other materials that have been activated, the othermaterial being selected to enhance the combustion process or to effectother desirable chemical reactions.

In embodiments, more than two components can be complexed together usingthe foregoing systems and methods. One can therefore produce complexesof multiple materials designed to have desirable properties, such asmore efficient combustion. For example, in an embodiment, lignin andcoal dust can each be treated with PDAC while starch is activated withhydrolyzed polyacrylamide. When the dispersions of each component arebrought together, a ternary complex can be formed, with lignin/coalcommingled and “glued” with starch particles that later expand underheat. The surface monolayer interaction among all the components servesto bind them together and to provide cohesive strength to the pelletcomposite. In an embodiment, lignin and coke particles can be complexedwith starch particles using these systems and methods.

In other embodiments, lignin and coal or coke can be combined ascomplexes without using coated starch particles. The lignin particlescan be used as anchor particles, to be coated with a tethering agent;the coal slurry (dilute or otherwise) can be pretreated with thecomplementary activator polymer. When the two fluid streams arecombined, spontaneous aggregation ensues.

In yet other embodiments, these systems and methods can be used toproduce composite pellets containing inorganic solids. For example,alkaline solids (e.g., calcium oxide or magnesium oxide) can becompounded into the composite pellets. During pellet combustion, theaforesaid inorganic materials are converted to the respective carbonate,thus sequestering products of coal combustion such as CO₂ and H₂S. Thusthe pelletized coal-based fuel formed in accordance with these systemsand methods are able to capture some of their own undesirable combustionbyproducts. Hence, pellets or other coal-based energy sources (e.g.,briquettes) can be made to absorb noxious volatile products ofcombustion, an advantageous property for applications in closed spaces,or example, or in situations where pollution concerns are of particularimportance.

5. Exemplary Applications

a. Tailings Processing

Extraction of minerals from ores can produce fine, positively chargedparticles of clay or other materials that remain suspended in theeffluent fluid stream. The effluent fluid stream can be directed to amechanical separator such as a cyclone that can separate the fluidstream into two components, an overflow fluid comprising fine tails thatcontains the fine (<approximately 50 micron) particles, and an underflowfluid stream that contains coarse tails, mainly sand, with a smallamount of fine clay particles.

In embodiments, the systems and methods disclosed herein can treat eachfluid stream, an overflow fluid and/or an underflow fluid. An activatingagent, such as a polyanion as described above, can preferably beintroduced into the overflow fluid stream, resulting in a flocculationof the fine particles therein, often forming a soft, spongy mass. Theunderflow fluid can be used for the preparation of tether-bearing anchorparticles. However, it will be clear that other sources for anchorparticles (e.g., sand) can also be used. In certain tailings fluids, thesand within the underflow fluid itself can act as an “anchor particle,”as described above. A cationic tethering agent, as described above, canbe introduced into the underflow fluid so that it self-assembles ontothe surface of the anchor particles, creating a plurality oftether-bearing anchor particles.

Following this treatment to each fluid stream, the two fluid streams canbe re-mixed in a batch, semi-batch or continuous fashion. Thetether-bearing anchor particles can interact, preferablyelectrostatically, with the activated, preferably flocculating, fineparticles, forming large agglomerations of solid material that can bereadily removed from or settled in the resulting fluid mixture.

In embodiments, the aforesaid systems and methods are amenable toincorporation within existing tailings separation systems. For example,a treatment process can be added in-line to each of the separate flowsfrom the overflow and underflow fluids; treated fluids then re-convergeto form a single fluid path from which the resulting agglomerations canbe removed. Removal of the agglomerations can take place, for example,by filtration, centrifugation, or other type of mechanical separation.

In one embodiment, the fluid path containing the agglomerated solids canbe subsequently treated by a conveyor belt system, analogous to thosesystems used in the papermaking industry. In an exemplary conveyor beltsystem, the mixture of fluids and agglomerated solids resulting from theelectrostatic interactions described above can enter the system via aheadbox. A moving belt containing a mechanical separator can movethrough the headbox, or the contents of the headbox are dispensed ontothe moving belt, so that the wet agglomerates are dispersed along themoving belt. One type of mechanical separator can be a filter with apore size smaller than the average size of the agglomerated particles.The size of the agglomerated particles can vary, depending upon the sizeof the constituent anchor particles (i.e., sand). For example, forsystems where the sand component has a size between 50/70 mesh, an 80mesh filter can be used. Other adaptations can be envisioned by artisanshaving ordinary skill in the art. Agglomerated particles can betransported on the moving belt and further dewatered. Water removed fromthe agglomerated particles and residual water from the headbox fromwhich agglomerates have been removed can be collected in whole or inpart within the system and optionally recycled for use in subsequentprocessing.

In embodiments, the filtration mechanism can be an integral part of themoving belt. In such embodiments, the captured agglomerates can bephysically removed from the moving belt so that the filter can becleaned and regenerated for further activity. In other embodiments, thefiltration mechanism can be removable from the moving belt. In suchembodiments, the spent filter can be removed from the belt and a newfilter can be applied. In such embodiments, the spent filter canoptionally serve as a container for the agglomerated particles that havebeen removed.

Advantageously, as the agglomerated particles are arrayed along themoving belt, they can be dewatered and/or dried. These processes can beperformed, for example, using heat, air currents, or vacuums.Agglomerates that have been dewatered and dried can be formed as solidmasses, suitable for landfill, construction purposes, or the like.

Desirably, the in-line tailings processing described above is optimizedto capitalize upon the robustness and efficiency of the electrostaticinteraction between the activated tailings and the tether-bearing anchorparticles. Advantageously, the water is quickly removed from the freshtailings during the in-line tailings processing, permitting itsconvenient recycling into the processing systems.

b. Remediation of Treatment Ponds

The systems and methods disclosed herein can be used for treatment oftailings at a facility remote from the mining and beneficiation facilityor in a pond. Similar principles are involved: the fluid stream bearingthe fine tailings can be treated with an anionic activating agent,preferably initiating flocculation. A tether-bearing anchor particlesystem can then be introduced into the activated tailings stream, or theactivated tailings stream can be introduced into a tether-bearing anchorparticle system. In embodiments, a tailings stream containing fines canbe treated with an activating agent, as described above, and applied toa stationary or moving bed of tether-bearing anchor particles. Forexample, a stationary bed of tether-bearing anchor particles can bearranged as a flat bed over which the activated tailings stream ispoured. The tether-bearing anchor particles can be within a container orhousing, so that they can act as a filter to trap the activated tailingspassing through it. On a larger scale, the tether-bearing anchorparticles can be disposed on a large surface, such as a flat or inclinedsurface (e.g., a beach), so that the activated tailings can flow overand through it, e.g., directionally toward a pond.

As an example, sand particles retrieved from the underflow fluid streamcan be used as the anchor particles to which a cationic tether isattached. A mass of these tether-bearing anchor particles can bearranged to create a surface of a desired thickness, forming an“artificial beach” to which or across which the activated tailings canbe applied. As would be appreciated by those of ordinary skill in theart, the application of the activated tailings to the tether-bearinganchor particles can be performed by spraying, pouring, pumping,layering, flowing, or otherwise bringing the fluid bearing the activatedtailings into contact with the tether-bearing anchor particles. Theactivated tailings are then associated with the tether-bearing anchorparticles while the remainder of the fluid flows across the surface andinto a collection pond or container.

In embodiments, an adaptation of the activator-tether-anchor systemsdisclosed herein can be applied to the remediation of existing tailingsponds for mining operations. Tailings ponds can comprise differentlayers of materials, reflecting the gravity-induced settlement of freshtailings after long residence periods in the pond. For example, the toplayer in the tailings pond can comprise clarified water. The next layeris a fluid suspension of fine particles like fine tailings. The fluidbecomes denser and denser, often settling into a stable suspension offluid fine tailings that has undergone self-weightconsolidation/dewatering, where the suspended particles have not yetsettled out. The bottom layer is formed predominately from material thathas settled by gravity. Desirably, the strata of the tailings pondcontaining suspended particles can be treated to separate the water thatthey contain from the fine particles suspended therein. The resultantclarified water can be drawn off and the solid material can bereclaimed. This could reduce the overall size of the tailings ponds, orprevent them from growing larger as fresh untreated tailings are added.

In embodiments, the systems and methods disclosed herein can be adaptedto treat tailings ponds. In an embodiment, an activating agent, forexample, one of the anionic polymers disclosed herein can be added to apond, or to a particle-bearing layer within a tailings pond, such as byinjection with optional stirring or agitation. Tether-bearing anchorparticles can then be added to the pond or layer containing theactivated fine particles. For example, the tether-bearing anchorparticles can be added to the pond from above, so that they descendthrough the activated layer. As the activated layer is exposed to thetether-bearing anchor particles, the flocculated fines can adhere to theanchor particles and be pulled down to the bottom of the pond bygravity, leaving behind clarified water. The tailings pond can thus beseparated into two components, a top layer of clarified water, and abottom layer of congealed solid material. The top layer of clarifiedwater can then be recycled for use, for example in further oreprocessing. The bottom layer of solids can be retrieved, dewatered andused for construction purposes, landfill, and the like.

c. Treating Waste or Process Streams

Particles modified in accordance with these systems and methods may beadded to fluid streams to complex with the particulate matter suspendedtherein so that the complex can be removed from the fluid. Inembodiments, the modified particles and the particulate matter mayinteract through electrostatic, hydrophobic, covalent or any other typeof interaction whereby the modified particles and the particulate matterform complexes that are able to be separated from the fluid stream. Themodified particles can be introduced to the process or waste streamusing a variety of techniques so that they complex with the particulatematter to form a removable complex. A variety of techniques are alsoavailable for removing the complexes from the fluid stream. For example,the modified particles can be mixed into the stream and then separatedvia a settling process such as gravity or centrifugation. If buoyant orlow-density modified particles are used, they can be mixed with thestream and then separated by skimming them off the surface. In anothermethod, the process stream could flow through a bed or filter cake ofthe modified particles. In any of these methods, the modified particlesinteract with the fine particulates and pull them out of suspension sothat later separation removes both modified particles and fineparticulates.

The particles described herein can be utilized to sequester and suspendfines and pollutants from waste tailings. The technology can be used forthe treatment of waste slurry as it is generated or can be used for theremediation of existing tailings ponds. As discussed below, massiveamounts of waste tailings are generated in the course of energyproduction and other mining endeavors. Such wastes or waste fluids caninclude, but are not limited to, oilfield drilling waste, fine coaltailings and coal combustion residues. Mining endeavors producing wastesand waste fluids include, but are not limited to, processing andbeneficiation of ores such as bauxite, phosphate, taconite, kaolin,trona, potash and the like. Mining endeavors having a waste slurrystream of fine particulate matter, can also include without limitationthe following mining processes: sand and gravel, nepheline syenite,feldspar, ball clay, kaolin, olivine, dolomite, calcium carbonatecontaining minerals, bentonite clay, magnetite and other iron ores,barite, and talc.

As examples, the systems and methods disclosed herein can be applied towaste materials such as would be produced by drilling in oil fields, bymining for coal, by burning coal, or by mining other organic materials.Oilfield drilling wastes include rock cuttings, drilling fluids, wellstimulation/fracturing fluids, brines, and petroleum residual. In a 1995survey, 68% of these wastes were disposed onsite by evaporation inretention ponds and burial. The majority of drilling fluids are held inopen pits, but the trend is towards a closed system with a storage tankreplacing the reserve pit. Fine coal tailings are a waste product ofcoal preparation plants, where coal is crushed and washed to make asuitable fuel with low sulfur and ash content. The washing processgenerates a slurry of finely divided particles of clay, coal, and otherimpurities. This material has accumulated as hundreds of ponds in coalproducing areas, often resulting in accidental discharges. Coalcombustion products include fly ash, bottom ash, boiler slag, flue gasdesulfurization material, and other scrubber wastes. The coal ash floodof December 2008 released 300 million gallons of fly ash sludge andwater from a TVA coal fired power plant, damaging 15 homes in Kingston,Tenn. and polluting the Emory River. A number of inorganic minesgenerate waste materials in fluid streams that can also be separatedusing the systems and methods disclosed herein.

1) Coal Mining Waste

Coal as it is recovered from the mine (termed “run-of-mine” or ROM coal)comes in a variety of sizes and shapes and contains mineral impuritiesfrom which it must be separated. Preparing the ROM coal for other uses,involving processes known as coal preparation or cleaning, aims to sortthe coal according to size, and aims to separate it from its mineralcontent. The mineral content of coal is the noncombustible inorganicfraction, comprised of minerals that are either detrital or authigenicin origin and that are introduced into the coal in the first or secondphases of coalification. Minerals can be found in the ROM coal ascombinations of larger inclusions within the coal lumps and ultrafinecrystals disseminated throughout the coal lumps.

As a first step in coal cleaning, the coal is crushed to reduce its sizeand to free it up from the larger mineral inclusions. Assisting in thisprocess is the fact that the coal tends to break more easily than theminerals, so that the coal can be liberated from some of the surroundingminerals by size reduction techniques using crushers, rotary breakers orother similar devices. Size differences are exploited to sort thecrushed coal into different categories of pellet sizes, some of whichcan be used immediately if the coal is of sufficient quality. Inaddition, the larger lumps of coal (˜10-150 mm in length) can be treatedwith a technology called dense-medium separation, where the organic coalis floated free of impurities by immersing the crushed material in ahigh-density liquid; because the coal is less dense, it floats to thesurface, while the heavier mineral matter will sink to be removed aswaste.

Further crushing may be necessary if the coal is more intimatelyassociated with minerals. The smaller-sized coal fragments can then betreated with froth flotation to separate the coal from the minerals thatsurround it. Using this technique, fine coal fragments can be mixed withwater and other additives to form a slurry, which is then exposed tostreams of air bubbles introduced into the mixture. The coal is carriedto the surface in the froth, where it can be skimmed off, screened anddewatered for commercial uses, while the minerals sink to the bottom.The dewatered mass of fine coal obtained through this process is termedFC, for “filter cake.” Coal particles in the filter cake are typicallyabout the size of sand particles.

The mineral material separated from the coal during these processes isdewatered, using for example vibratory screens, and then compacted fordisposal or for further mineral recovery efforts. This waste mineralmaterial is called coal refuse, or coal processing refuse (CPR).Depending on the type and source of the coal, the ratio of CPR to filtercake can be as high as 5:1 by weight. It may contain particles thatrange from microns in size to millimeters in size. The CPR may befurther treated to remove useful minerals from it, or it may be disposedof as a waste material.

After these water-driven separation processes, fine particles remain inthe slurry, called “fines.” The fines from coal processing are similarin behavior to the fines produced by coal extraction. Fine materialsgenerated from such mining activities are often found well-dispersed inaqueous environments, such as wastewater. The finely dispersed materialsfrom coal mining, termed “coal fines,” are suspended in water duringcoal extraction and processing. Separating the coal fines from thesuspending medium is difficult, as the fines tend to remain suspendedunless energy-intensive processes are employed to recover them. In coalmining and processing, significant quantities of coal fines are createdthat require disposal and handling. About 15-20% of the mined tonnagecan be left as residual fines, in sizes ranging from powder to smallgranules. There is presently no direct utility for these fines, so thatthey are a source of waste and inefficiency in the industry. Moreover,their handling and storage are hazardous and expensive.

Coal fines can be converted into pellets to facilitate disposal,transportation and handling. Coal-fired power plants can burn coalpellets as the fuel of choice. Pelletizing the coal fines generallyrequires adding an adhesive binder to the slurry containing coal fines,and using high temperatures or pressures to form the dry, consolidatedpellets. Such steps are typically employed to agglomerate coal becausecoal particles do not naturally adhere to each other unless particlesize is carefully controlled and extremely high pressures are used (over20,000 psi for bituminous coal, for example). As an alternative to highpressure, an adhesive binder such as asphalt can be applied to bind thecoal particles together. The adhesive can be expensive itself, and itsuse requires that a system incorporate equipment specifically to prepareand meter the adhesive, adding additional expense.

Pellet manufacture presently requires both shaping and drying.Water-soluble or water-dispersible binders are difficult to dry, and theresulting pellets are difficult to dewater. Once in pellet form, thecoal product is densely consolidated, so that oxygen for combustionpenetrates with difficulty. In other words, the high interfacial areacharacteristic of fines is drastically reduced by pellet formation, andthe great combustion efficiency inherent in powder burning is lost.

Currently, then, pelletization permits fines to be disposed of in a formthat is useful for combustion purposes and convenient for transport andhandling. However, the pellets do not burn efficiently in a combustionchamber. It is known in the art to coat wet pellets with a hydrophobicmaterial during processing so that residual water is trapped in theinterior of the pellet; when such pellets are introduced into a boiler,the interior water vaporizes rapidly so that the pellet bursts,releasing powdered coal for combustion. However, the high heat ofvaporization for water lowers the overall power output of a plant usingsuch technology. In addition, a coating step is required, adding to theexpense of manufacturing.

In addition to coal fines waste, an enormous amount of biomass waste isgenerated annually. Wood waste is produced by lumber mills, for example,with wasted wood accounting for about ten percent of processed lumber.Wood waste can also be found in forests as deadwood, living biomass, orresidua from timber harvesting. Lignocellulosic waste is produced byagriculture (e.g., corn stalks, wheat, hays, grasses, sugar canebagasse, soybeans) and by processing (e.g., cotton gins). Feathersremaining from poultry farming require disposal as waste. Waste fromanimal husbandry includes organic material such as manure, feedstock andbedding. Additional organic waste is produced by cattle, hog, chicken,turkey and fish farming. Industrial products such as carpeting andautomobile tires end up as waste that must be disposed of.

In embodiments, the systems and methods disclosed herein can use coalfrom coal processing sources to remove coal fines from a mixture andform a coal-on-coal composite particle. In embodiments, coal from filtercake can be used to attract, consolidate and/or organize coal fines inmixtures, thereby forming a composite particle substantially formed fromcoal. Such a composite particle, advantageously, can be an efficientsource of energy. In embodiments, composite coal-on-coal particles canbe formed that are then combined with other adulterants such as sand,minerals or water to decrease the energy content of the final product.Such modification may be carried out, for example, to meet thespecifications of a particular customer for an energy source deliveringa known quantity of energy. In certain cases, for example, a customer'scontract calls for receiving a coal-based energy source that provides1200 BTU per ton; if the composite coal-on-coal particle pellets provide1300 BTU per ton, they can be adulterated so that the delivered energycontent is lowered.

In embodiments, the systems and methods disclosed herein can useparticulate waste material from coal processing to remove coal finesfrom a mixture and form a composite particle. In embodiments, wastematerials such as that found in coal processing refuse (CPR) or othermineral wastes can be used to attract, consolidate and/or organize coalfines in mixtures, forming composite particles with the coal fines thatput the waste materials to beneficial uses. In embodiments, thesesystems and methods have the advantage of using materials (whetherenergy-yielding like the coal in filter cake (FC) or non-energy-yieldinglike the minerals in CPR or other waste materials) that are foundabundantly on site where coal is mined and processed.

In accordance with these systems and methods, FC and CPR can be used asanchoring particles for treating coal fines dispersed in slurries in aprocess that is rapid and robust, yielding clarified water andgeotechnically stable solids that are easy to handle and stackable.These systems and methods can result in near-immediate recovery of coalfines from aqueous suspensions, producing solids that have very lowinitial (i.e., pre-drying) moisture levels. Sequestration of coal finesas composite particles with CPR can allow stockpiling and disposal ofthis waste material. Sequestration of coal fines as composite particleswith FC can produce combustible pellets that can convert energy sourcesnow discarded into useable fuel.

In embodiments, the systems and methods disclosed herein can use theactivator-tether-anchor particle (ATA) technology for pelletizing coalto yield pellets that are dense during handling and transport, but thatcombust efficiently and completely. In preparing pellets from coalfines, dewatering takes place spontaneously, rapidly and substantiallycompletely; in embodiments, heat and/or pressure is not required. Thedewatering process exploits strong molecular forces between chargedspecies.

In embodiments, the pellets can become porous upon exposure to heat,achieving the high combustion efficiency found in powdery fuel. In suchembodiments, the porosity can be imparted due to heat-induced foaming ofcomponents within the pellet matrix. The disclosed systems and methodscan produce a pellet comprising components that expand upon heating,creating interior pores and channels that allow oxygen penetration. Sucha highly perforated and expanded structure can optimize combustion. Theself-expanding feature of the pellets contributes to combustionefficiency by virtue of its behavior as a de facto oxygenator. Inembodiments, oxygen for combustion with the pellets can be taken up bycoal particle surfaces by diffusion through the heat-induced porosity ofthe pellet matrix, and by fragmentation of the matrix structure.

Pellets in accordance with these systems and methods are suitable foruse in, for example, power generation facilities. The enhancedefficiency of the instant pellets can yield greater power generation,and less unwanted byproducts (e.g., various noxious effluent gasesand/or colloidal solids).

In accordance with these systems and methods, pellets can be producedthat are composites of coal and biomass. In embodiments, compositepellets can be formed having a self-expanding feature that createsporosity, so that the pellets can undergo efficient combustion. Finallythe process consolidates coal slurry without the need of intricatemechanical assist and the expelled water is clarified. Fines originallydispersed in the slurry are nearly completely captured and incorporatedinto the pellets.

In embodiments, the systems and methods disclosed herein can enhance thesettlement rate of dispersed coal fines materials by incorporating themwithin a coarser particulate matrix, so that coal solids can be removedfrom aqueous suspension as a material suitable for pelletizing. Thesystems and methods disclosed herein involve three components: preparingtether-bearing anchor particles, activating the coal fines, andcomplexing the activated coal fines with the tether-bearing anchorparticles to form a removable complex.

In embodiments, the systems and methods disclosed herein can remove coalfines from a fluid, where the fluid contains a population of suspendedcoal fines. The system comprises an activator polymer added to the fluidto complex with the suspended coal fines to form activated coal fines,the activated coal fines residing within the fluid volume, and furthercomprises an anchor particle complexed with a tethering agent to formtether-bearing anchor particles. In this system, the tether-bearinganchor particles are mixed with the fluid volume to contact theactivated coal fines, the tether-bearing anchor particles being capableof complexing with the activated coal fines to form complexes removablefrom the fluid. In accordance with this system, the complexes removablefrom the fluid comprise a composite material that includes complexedcoal fines and anchor particles. In embodiments, the anchor particlecomprises biomass. In embodiments, the anchor particle comprises starch.In embodiments, the anchor particle comprises a combustible material. Inembodiments, the methods for removing coal fines from a fluid compriseproviding an activator polymer capable of interacting with a populationof coal fines suspended in a fluid; adding the activator polymer to thepopulation to form activated coal fines; providing an anchor particle;complexing the anchor particle with a tethering agent capable ofcomplexing with the activated coal fines, thereby forming tether-bearinganchor particles; mixing the tether-bearing anchor particles with theactivated coal fines to form a complex removable from the fluid, thecomplex comprising a composite material comprising coal fines and anchorparticles, and removing the composite material from the fluid. Inembodiments, the anchor particle comprises biomass or starch orcombustible materials.

In accordance with these systems and methods, energy-bearing pellets canbe produced that are composite materials comprising an energy-containingfine material and a combustible anchor particle in a complex. Thecomplex can include an interacting pair of polyelectrolytes, wherein thefirst of the pair of polyelectrolytes is bound to the energy-containingfine material and the second of the pair of polyelectrolytes is bound tothe combustible anchor particle. In embodiments, the energy-containingfine material comprises coal fines. In embodiments, the anchor particlecomprises biomass or starch.

2) Coal Combustion Products

One of the significant wastes produced during coal combustion is flyash. The ash content of coal can range from 5 wt % for high-grade coalup to 50 wt % for poor quality coal. Over 131 million tons of fly ash isgenerated annually in the US alone. Current regulations mandate that flyash be captured from exhaust gas streams, typically by electrostaticprecipitators.

Fly ash is primarily composed of silicon dioxide, aluminum oxide, ironoxides, and calcium oxide, though its composition varies depending onthe input coal and combustion conditions. Fly ash particles are usuallyspherical with diameters in the range of 0.1-100 μm. Depending on thecomposition of the fly ash, it may possess pozzolanic or evenself-cementing properties. These properties allow fly ash to be reusedin concrete, embankments, and a variety of building and constructionmaterials.

Up to 47% of fly ash generated in the US ends up being beneficiallyreused. The remaining 53% of fly ash generated in the US is disposed ofin landfills (in dry powder-like form) or in massive man-madeimpoundment areas (in slurry form). Problems with landfill disposalinclude seepage into the environment and the ability of the fly ash tobecome airborne in the form of hazardous dusts. Trace amounts of toxicelements are frequently present in fly ash, including but not limited tothe following: arsenic, barium, chromium, lead, manganese, selenium,strontium, and zinc. Slurry impoundment avoids dust issues; howevergroundwater contamination can occur and, more significantly, massive andimmediate environmental damage can occur if an impoundment dam ruptures.A prime example occurred in 2008 when a Tennessee Valley Authority flyash impoundment dam ruptured and released approximately 1.1 billiongallons of fly ash slurry into the environment.

In embodiments, the systems and methods disclosed herein can be used toconsolidate the fine coal combustion products like fly ash. A fluidstream containing the fly ash or similar fine particles can be treatedwith an activator, and a tether-bearing anchor particle can be added tothe activated fluid stream. The activator binds to the fine particles,and the tethers on the anchor particles binds to the activator-fineparticle units. A complex is formed between the activator-fine particleunits and the tether-bearing anchor particles. Such complexes can bereadily removed from the fluid stream. Few alternative disposaltechniques exist for fly ash.

3) Inorganic Mining Waste

A number of mining operations yield wastewater streams containing fineparticles produced during the processing or beneficiation of ores. As anexample, the production of aluminum from bauxite ore according to thecommonly-used Bayer process takes place by treating the crushed orground ore with a hot sodium hydroxide solution to produce alumina(Al₂O₃), which can be reduced to yield aluminum. The insoluble part ofthe bauxite ore is carried away as an alkaline aqueous slurry called“red mud.” Red mud is a complex material with characteristics thatdepend on the bauxite from which it is derived, and on the processparameters that produce it. Common characteristics of red mud include awater suspension of fine particles suspended in a highly alkaline watersolution, mainly composed of iron oxides, but having a variety ofelements and mineralogical phases. The red mud fluid stream, containingabout 7-9% solids, is typically sequestered in a containment area (anold excavated mine or a manmade lake called a tailings pond) so that thesolids can settle out by gravity. About two tons of red mud is producedper ton of metallic aluminum. The magnitude of red mud associated withaluminum production poses a significant environmental challenge forcountries where bauxite is refined. A small country like Jamaica, forexample, where bauxite refinement is a leading industry, lacks open landsuitable for disposal of the hazardous red mud; moreover, containmentproblems such as leakage, groundwater seepage and rupture of tailingspond dikes makes disposal of this material even more hazardous.

As another example, iron is produced from an ore called taconite thatcontains magnetite, an amalgam of iron oxides with about 25-30% iron. Toextract the iron from the ore, the ore is crushed into fine particles sothat the iron can be removed from the non-ferromagnetic material in theore by a magnetic separator. The iron recovered by the magneticseparator is then processed into “pellets” containing about 65% ironthat can be used for industrial purposes like steel-making. Ore materialnot picked up by the magnetic separator is considered waste material, organgue, and is discarded. Gangue typically includes non-ferrous rocks,low-grade ore, waste material, sand, rock and other impurities thatsurround the iron in the ore. For every ton of pellets produced, about2.7 tons of gangue is also produced. The waste is removed from thebeneficiation site as a slurry of suspended fine particles, termedtailings. About ⅔ of the tailings are classified as “fine tailings,”composed of extremely fine rock particles more than 90% of which aresmaller than 75 microns, or −200 mesh); typically, the fine tailingsthey have little practical use at the mines, and end up sequestered incontainment areas such as tailings ponds.

Another mining operation with similar wastewater handling issues is theproduction of kaolin. Kaolin (“china clay”) is a white claylike materialcomposed mainly of a hydrated aluminum silicate admixed with other clayminerals. Kaolin, used for a variety of industrial applications, ismined and then processed; dry processes and wet processes are available.Wet processes, used extensively to produce additives for the paperindustry, yield a slurry that is fractionated into coarse and finefractions using a variety of mechanical means like centrifuges,hydrocyclones and hydroseparators. Despite repeated processing, afraction of the slurry contains fine particulate kaolin that cannot beseparated from other fine particulate waste residues. This material isdeemed waste, and is sequestered in containment areas, either manmadelagoons or spent kaolin mines.

Trona (trisodium hydrogendicarbonate dihydrate) is a mineral that ismined in the United States as a source of sodium carbonate. After thetrona is mined, it is processed by exposing it to aqueous solvents sothat the sodium carbonate can be recovered. The insoluble materials inthe trona, including oil shales, mudstone and claystone, is carried awayas tailings for disposal. Tailings, containing suspended fine particlesin a fluid stream, may be transported to confinement areas, liketailings ponds; alternatively, tailings may be pumped into abandonedareas of the mine, with retaining walls or other barriers beingconstructed as needed to prevent the tailings from entering mine areasthat are still active.

Phosphatic ore (fluorapatite) mining is a major worldwide industry, withover 150 million tons of ore mined annually. Domestic mining producesaround 30 million tons of ore, about 75% of which comes from Florida.During the extraction of phosphate from the mined ore, a process calledbeneficiation, significant quantities of waste clay and sand aregenerated. The approximate ratio of the extracted ore is 1:1:1 offluorapatite to clay to sand. Thus, with the 30 million tons of orebeing mined, around 10 million tons of waste clay and 10 million tons ofwaste sand must be disposed of annually in the U.S.

The clay that is produced by beneficiation exists in a 3-5% (by weight)slurry. The current practice of clay disposal is to store the clayslurry in large ponds known as clay settling areas (CSAs), where theclay is allowed to separate from the water suspension by gravity overlong periods of time, i.e., several decades. For a typical phosphatemine, up to 60% of the surface area of the mine ends up as CSAs.Estimates are that around 5,000 acres of land is turned into CSAsannually in central Florida. Left untreated it can take several decadesbefore CSAs become stable enough for reuse to be considered. Because ofthe huge environmental and economic impacts of CSAs, a simple, robust,and cost-effective method for treating the clay slurry waste is needed.

While other methods for separating clay fines from wastewater slurrieshave been tried for phosphate mining, they have proven to be difficultand costly. For example, the Dewatering Instantaneously with PulpRecycle (DIPR) process has been under investigation for over 20 years atthe Florida Institute of Phosphate Research (FIPR), disclosed in U.S.Pat. No. 5,449,464. According to this disclosure, clay slurry is treatedwith a flocculant and a pulp material to dewater the slurry. While thisapproach has been studied for over two decades, its high cost, partlydue to capital costs of equipment to dewater the treated slurry to highsolids content, has prevented its adoption. There remains a need in theart, therefore, for an effective and economical approach to treating theclay-bearing wastewater slurry that is produced during phosphatebeneficiation.

Research in treating wastewater produced by extracting bitumen from oilsands ore has demonstrated that tailings from these operations can betreated in a three-step process to consolidate suspended clay fines intosolid masses that can be readily removed from the fluid stream. Thesesystems and methods are disclosed in International Application No.:PCT/US09/54278, the entire teachings of which are hereby incorporated byreference herein. Modifications of such systems and methods can beadvantageously applied to the treatment of fluid wastewater streams thatbeneficiation processes for mined ores produce.

In embodiments, the systems and methods disclosed herein can be appliedto the treatment of wastewater streams containing fine particlesproduced during the processing or beneficiation of ores. The systems andmethods disclosed herein can be combined with routine modifications ofthe fluid stream in anticipation of treatment, in the course oftreatment, or following treatment. For example, pH adjustments of thefluid stream can be carried out. In embodiments, the systems and methodsdisclosed herein can be adapted to and optimized for the needs of aspecific mining industry for treatment of particulate suspensions influid streams of waste products.

For example, following the production of aluminum, e.g., from bauxiteore according to the commonly-used Bayer process, the insoluble part ofthe bauxite ore is carried away as an alkaline aqueous slurry called“red mud.” Red mud typically comprises a water suspension of fineparticles suspended in a highly alkaline water solution, mainly composedof iron oxides, but having a variety of elements and mineralogicalphases. The fluid stream can be treated with an activator in accordancewith these systems and methods, and can be contacted with tether-bearinganchor particles. As a result of this treatment, the fines in the fluidstream can be sequestered as solids and separated from the fluid itself.In embodiments, the sequestered solids can be consolidated into a massthat can be used for a variety of beneficial applications. Inembodiments, anchor particles can be used that are indigenous to themining area, or that are economically introduced into the mining areafor use with these processes.

As another example, the systems and methods disclosed herein can beapplied to waste produced during the beneficiation of iron, for example,iron produced from taconite. As iron is produced from the ore, wastematerial called gangue is generated. The gangue is removed from thebeneficiation site as a slurry of suspended fine particles, termedtailings. About ⅔ of the tailings are classified as “fine tailings,” awaste material suitable for treatment by the systems and methodsdisclosed herein. In embodiments, the fluid stream containing the finetailings can be treated with an activator in accordance with thesesystems and methods, and can be contacted with tether-bearing anchorparticles. As a result of this treatment, the fines in the fluid streamcan be sequestered as solids and separated from the fluid itself. Inembodiments, the sequestered solids can be consolidated into a mass thatcan be used for a variety of beneficial applications. In embodiments,anchor particles can be used that are indigenous to the mining area, orthat are economically introduced into the mining area for use with theseprocesses.

As another example, the systems and methods disclosed herein can beapplied to waste produced during the beneficiation of kaolin. Theprocessing of kaolin yields a slurry that can be separated into afraction that contains fine particulate kaolin that cannot be readilyremoved from the fluid stream. This fluid stream is suitable fortreatment by the systems and methods disclosed herein. In embodiments,the fluid stream containing the fine tailings can be treated with anactivator in accordance with these systems and methods, and can becontacted with tether-bearing anchor particles. As a result of thistreatment, the fines in the fluid stream can be sequestered as solidsand separated from the fluid itself. In embodiments, the sequesteredsolids can be consolidated into a mass that can be used for a variety ofbeneficial applications. In embodiments, anchor particles can be usedthat are indigenous to the mining area, or that are economicallyintroduced into the mining area for use with these processes.

As another example, the systems and methods disclosed herein can beapplied to the waste produced during the mining of trona. Following themining and beneficiation of trona, insoluble materials carried away aswaste can include fine particulate tailings transported in a fluidstream. This fluid stream is suitable for treatment by the systems andmethods disclosed herein. In embodiments, the fluid stream containingthe fine tailings can be treated with an activator in accordance withthese systems and methods, and can be contacted with tether-bearinganchor particles. As a result of this treatment, the fines in the fluidstream can be sequestered as solids and separated from the fluid itself.In embodiments, the sequestered solids can be consolidated into a massthat can be used for a variety of beneficial applications. Inembodiments, anchor particles can be used that are indigenous to themining area, or that are economically introduced into the mining areafor use with these processes.

As another example, the systems and methods disclosed herein can beapplied to the waste produced during the mining of phosphate. During thebeneficiation of phosphate ore, waste materials including fine clayparticles (clay fines) are produced and are carried away in a fluidwaste stream or slurry. This fluid stream is suitable for treatment bythe systems and methods disclosed herein. In embodiments, the fluidstream containing the fine tailings can be treated with an activator inaccordance with these systems and methods, and can be contacted withtether-bearing anchor particles. As a result of this treatment, thefines in the fluid stream can be sequestered as solids and separatedfrom the fluid itself. In embodiments, the sequestered solids can beconsolidated into a mass that can be used for a variety of beneficialapplications. In embodiments, anchor particles can be used that areindigenous to the mining area, or that are economically introduced intothe mining area for use with these processes.

In embodiments, for example, the systems and methods disclosed hereinprovide methods for treating and disposing of phosphatic clays, inconjunction with the sand waste also generated during phosphatic orebeneficiation. In other embodiments, the systems and methods disclosedherein provide methods for treating and disposing of fines collectedfrom tailings streams. Advantageously, coarse waste from miningoperations can be used as anchor particles, or waste-like materials(sand, crushed rock, or other waste materials) can be brought on-site tobe used for anchor particles.

As another example, potash mining operations result in wastewaterhandling issues that can be advantageously addressed with the systemsand methods disclosed herein. Potash is the general name for potassiumsalts, including potassium carbonate, and is mined for agricultural(fertilizer) use. A large portion of the mined potash ore ends up as awaste, either as a solid or slurry, called potash tailings. The potashtailings slurry is an aqueous saturated salt/brine stream that containswaste ore, clays, and other fine materials. The most common method fordisposal is to pump the potash tailings into above-ground impoundmentareas or mined underground pits. The large volumes of tailings and highsalinity pose significant disposal issues. Additionally, large amountsof salt simply end up in these waste streams. Environmental concerns areadding increased pressure for potash mining companies to findalternatives to tailings ponds as a disposal practice.

A number of other mining operations produce fine particulate wastecarried in fluid streams. Such fluid streams are suitable for treatmentby the systems and methods disclosed herein. Modification of the fluidstream before, during or after application of these systems and methodsmay be advantageous. For example, pH of the fluid stream can beadjusted. Examples of additional mineral mining operations that have awaste slurry stream of fine particulate matter can include the followingmining processes: sand and gravel, nepheline syenite, feldspar, ballclay, kaolin, olivine, dolomite, calcium carbonate containing minerals,bentonite clay, magnetite and other iron ores, barite, and talc.

EXAMPLES Examples 1-7

The following materials were used in the Examples 1-7 below:

-   -   Washed Sea Sand, 50+70 Mesh, Sigma Aldrich, St. Louis, Mo.    -   Chitosan CG 800, Primex, Siglufjodur, Iceland    -   Branched Polyethyleneimine (BPEI) (50% w/v), Sigma Aldrich, St.        Louis, Mo.    -   Polyvinyl Amine—Lupamin 1595, Lupamin 9095, BASF, Ludwigshafen,        Germany    -   Poly(diallyldimethylammonium chloride) (pDAC) (20% w/v), Sigma        Aldrich, St. Louis, Mo.    -   FD&C Blue #1, Sigma Aldrich, St. Louis, Mo.    -   Hydrochloric Acid, Sigma Aldrich, St. Louis, Mo.    -   Tailings Solution from a low-grade tar sand    -   Dicalite, Diatomaceous Earth, Grefco Minerals, Inc., Burney,        Calif.    -   3-Isocyanatopropyltriethoxysilane, Gelest, Morrisville, Pa.    -   Sodium Hydroxide, Sigma Aldrich, St. Louis, Mo.    -   Isopropyl Alcohol (IPA), Sigma Aldrich, St. Louis, Mo.

Example 1: BPEI Coated Diatomaceous Earth

Diatomaceous earth (DE) particles coupled with BPEI are created using asilane coupling agent. 100 g of DE along with 1000 mL isopropyl alcohol(IPA) and a magnetic stir bar is placed into an Erlenmeyer flask. 1 gm3-Isocyanatopropyltriethoxysilane is added to this solution and allowedto react for 2 hours. After 2 hours, 2 mL of BPEI is added and stirredfor an additional 5 hours before filtering and washing the particleswith IPA 2×'s and deionized water (DI water). The particles are thenfiltered and washed with a 0.12 M HCl solution in isopropanol (IPA) thendried.

Example 2: 1% Chitosan CG800 Stock Solution

The chitosan stock solution is created by dispersing 10 g of chitosan(flakes) in 1000 mL of deionized water. To this solution is addedhydrochloric acid until a final pH of 5 is achieved by slowly andincrementally adding 12 M HCl while continuously monitoring the pH. Thissolution becomes a stock solution for chitosan deposition.

Example 3: Diatomaceous Earth—1% Chitosan Coating

10 g of diatomaceous earth is added to 100 mL deionized water with astir bar to create a 10% slurry. To this slurry is added 10 mL's of the1% chitosan stock solution of CG800. The slurry is allowed to stir for 1hour. Once the slurry becomes homogeneous the polymer is precipitatedout of solution by the slow addition of 0.1 N sodium hydroxide until thepH stabilizes above 7 and the chitosan precipitates onto the particlesof diatomaceous earth. The slurry is filtered and washed with a 0.05 MHCl solution in isopropanol (IPA) then dried.

Example 4: Particle Performance on Tailings Solution

Coated and uncoated diatomaceous earth particles were used inexperiments to test their ability to settle dispersed clay fines in anaqueous solution. The following procedure was used for each type ofparticle, and a control experiment was also performed where the particleaddition step was omitted.

One gram of particles was added to a centrifugation tube. Using asyringe, the centrifugation tube was then filled with 45 ml of tailingsolution containing dispersed clay. One more tube was filled with justthe tailings solution and no diatomaceous earth particles. The tube wasmanually shaken for 30 seconds and then placed on a flat countertop. Thetube was then observed for ten minutes allowing the clay fines to settleout.

Results:

No DE addition (control samples): Tailing solution showed no significantimprovement in cloudiness.

DE Coated with Chitosan: Tailing solution was significantly less cloudycompared to control samples.

DE Coated with BPEI: Tailing solution was significantly less cloudycompared to control samples.

DE Uncoated: Tailing solution showed no significant improvement incloudiness compared to control samples.

Example 5: Preparation of Polycation-Coated Washed Sea Sand

Washed sea sand is coated with each of the following polycations:chitosan, lupamin, BPEI, and PDAC. To perform the coating, an aqueoussolution was made of the candidate polycation at 0.01M concentration,based on its molecular weight. 50 g washed sea sand was then placed in a250 ml jar, to which was added 100 ml of the candidate polycationsolution. The jar was then sealed and rolled for three hours. Afterthis, the sand was isolated from the solution via vacuum filtration, andthe sand was washed to remove excess polymer. The coated sea sand wasthen measured for cation content by solution depletion of an anionic dye(FD&C Blue #1) which confirmed deposition and cationic nature of thepolymeric coating. The sea sand coated with the candidate polymer wasthen used as a tether-attached anchor particle in interaction with fineparticulate matter that was activated by treating it with an activatingagent.

Example 6: Use of Polymer-Coated Sea Sand to Remove Fine Particles fromSolution

In this Example, a 45 ml. dispersion of fine materials (7% solids) froman oil sands tailings stream is treated with an activating polymer(Magnafloc LT30, 70 ppm). The fines were mixed thoroughly with theactivating polymer. 10 gm of sea sand that had been coated with PDACaccording to the methods of Example 1 were added to the solutioncontaining the activated fines. This mixture is agitated and isimmediately poured through a stainless steel filter, size 70 mesh. Aftera brief period of dewatering, a mechanically stable solid is retrieved.The filtrate is also analyzed for total solids, and is found to have atotal solids content of less than 1%.

Example 7: Use of Sea Sand without Polymer Coating to Remove FineParticles from Solution (Control)

In this Example, a 45 ml. dispersion of fine materials (7% solids) istreated with an activating polymer (Magnafloc LT30, 70 ppm). The fineswere mixed thoroughly with the activating polymer. 10 gm of uncoated seasand were added to the solution containing the activated fines. Thismixture is agitated and is immediately poured through a stainless steelfilter, size 70 mesh. The filtrate is analyzed for total solids, and isfound to have a total solids content of 2.6%.

Examples 8-18

The following materials were used in Examples 8-18 below:

-   -   Commercially available poly(acrylamide) (50% hydrolyzed), 15M MW    -   Poly(diallyldimethylammonium chloride) (pDADMAC) (20% w/v),        Sigma Aldrich, St. Louis, Mo.    -   Coal slurry from a coal washing plant    -   Bagasse from the Louisiana sugar industry    -   Peanut shells from Whole Foods Grocery Store    -   Coal solids, 0.01-0.2 cm size fraction    -   Lignin powder, Sigma Aldrich, St. Louis, Mo.    -   Paper pulp from a bleached kraft mill    -   Corn starch Shaw's Grocery Store brand    -   Grass clippings from Cambridge, Mass.    -   Coal mine samples of filter cake and coal processing refuse.

Example 8: Activated Coal Slurry

Coal slurry was thoroughly mixed to ensure that a uniformly dispersed,homogeneous suspension is present. The coal slurry that was usedcontains 22% dry solids. To the slurry, an activator, 50% hydrolyzedpoly(acrylamide), was added to yield a 113 ppm (activator to coalsolids) concentration. The coal slurry with activator is gently mixeduntil visible flocculations (“flocs”) are formed.

Example 9: Activated Coal Slurry+Tethered Bagasse

Commercial bagasse was dried and mechanically chopped or blended toproduce solids of 1 cm in length or smaller. The dried, chopped bagassewas mixed with water and tethered with 500 ppm of pDADMAC. Activatedcoal slurry prepared in accordance with Example 8 was combined with thetethered bagasse in a ratio of 0.06:1 (bagasse to coal slurry drysolids). The tethered bagasse plus activated coal slurry solution wasmixed for ˜10 seconds and poured into a 250 mL graduated cylinder andallowed to settle for 15 minutes. The settling rate corresponded toapproximately 8 ft/hr. The bed height compacted to approximately 63% ofthe initial volume of the mixture, and the turbidity of the supernatantwas 221 Nephelometric Turbidity Units (NTU). A sample of thebagasse-coal solids was dabbed dry with paper towels, and the remainingwet solids contained approximately 54% dry solids. The solids can be airdried or dried by some other means to produce readily usable fuel.

Example 10: Activated Coal Slurry+Tethered Peanut Shells

Commercial peanut shells were mechanically chopped or blended to producesolids of 2 cm in size or smaller. The chopped peanut shells were mixedwith water and tethered with 500 ppm of pDADMAC. Activated coal slurryprepared in accordance with Example 8 was combined with the tetheredpeanut shells in a ratio of 0.06:1 (peanut shells to coal slurry drysolids). The tethered peanut shells plus activated coal slurry solutionwas mixed for ˜10 seconds and poured into a 250 mL graduated cylinderand allowed to settle for 15 minutes. The settling rate corresponded toapproximately 4 ft/hr. The bed height compacted to approximately 60% ofthe initial volume of the mixture, and the turbidity of the supernatantwas 27 NTU. A sample of the peanut shells-coal solids was dabbed drywith paper towels, and the remaining wet solids contained approximately51% dry solids. The solids can be air dried or dried by some other meansto produce readily usable fuel.

Example 11: Activated Coal Slurry+Tethered Coal

Coal chunks were mechanically crushed to produce solids of 0.2 cm inlength or smaller. The crushed coal was mixed with water and tetheredwith 500 ppm of pDADMAC. Activated coal slurry prepared in accordancewith Example 8 was combined with the tethered crushed coal in a ratio of0.51:1 (crushed coal to coal slurry dry solids). The tethered crushedcoal plus activated coal slurry solution was mixed for ˜10 seconds andpoured into a 250 mL graduated cylinder and allowed to settle for 15minutes. The settling rate corresponded to approximately 11 ft/hr. Thebed height compacted to approximately 56% of the initial volume of themixture, and the turbidity of the supernatant was 473 NTU. A sample ofthe coal-coal solids was dabbed dry with paper towels, and the remainingwet solids contained approximately 61% dry solids. The solids can be airdried or dried by some other means to produce readily usable fuel.

Example 12: Activated Coal Slurry+Tethered Lignin

Lignin powder was mixed with water and tethered with 500 ppm of pDADMAC.Activated coal slurry prepared in accordance with Example 8 was combinedwith the tethered lignin in a ratio of 0.51:1 (lignin to coal slurry drysolids). The tethered lignin plus activated coal slurry solution wasmixed for ˜10 seconds and poured into a 250 mL graduated cylinder andallowed to settle for 15 minutes. The settling rate corresponded toapproximately 6 ft/hr. The bed height compacted to approximately 65% ofthe initial volume of the mixture. A sample of the lignin-coal solidswas dabbed dry with paper towels, and the remaining wet solids containedapproximately 57% dry solids. The solids can be air dried or dried bysome other means to produce readily usable fuel.

Example 13: Activated Coal Slurry+Tethered Pulp

Commercial paper pulp was mixed with water overnight and tethered with500 ppm of pDADMAC. Activated coal slurry prepared in accordance withExample 8 was combined with the tethered paper pulp in a ratio of 0.58:1(wet pulp to coal slurry dry solids). The tethered pulp plus activatedcoal slurry solution was mixed for ˜10 seconds and poured into a 250 mLgraduated cylinder and allowed to settle for 15 minutes. The settlingrate corresponded to approximately 5 ft/hr. The bed height compacted toapproximately 71% of the initial volume of the mixture, and theturbidity of the supernatant was 109 NTU. A sample of the pulp-coalsolids was dabbed dry with paper towels, and the remaining wet solidscontained approximately 51% dry solids. The solids can be air dried ordried by some other means to produce readily usable fuel.

Example 14: Activated Coal Slurry+Tethered Starch

Commercial corn starch was mixed with water and tethered with 500 ppm ofpDADMAC. Activated coal slurry prepared in accordance with Example 8 wascombined with the tethered starch in a ratio of 0.53:1 (starch to coalslurry dry solids). The tethered starch plus activated coal slurrysolution was mixed for ˜10 seconds and poured into a 250 mL graduatedcylinder and allowed to settle for 15 minutes. The settling ratecorresponded to approximately 2 ft/hr. The bed height compacted toapproximately 69% of the initial volume of the mixture, and theturbidity of the supernatant was 803 NTU. A sample of the starch-coalsolids was dabbed dry with paper towels, and the remaining wet solidscontained approximately 56% dry solids. The solids can be air dried ordried by some other means to produce readily usable fuel.

Example 15: Activated Coal Slurry+Tethered Grass Clippings

Grass clippings were dried and mechanically chopped or blended toproduce solids of 1 cm in length or smaller. The dried, chopped grassclippings were mixed with water and tethered with 500 ppm of pDADMAC.Activated coal slurry prepared in accordance with Example 8 was combinedwith the tethered grass clippings in a ratio of 0.06:1 (grass clippingsto coal slurry dry solids). The tethered grass clippings plus activatedcoal slurry solution was mixed for ˜10 seconds and poured into a 250 mLgraduated cylinder and allowed to settle for 15 minutes. The settlingrate corresponded to approximately 7 ft/hr. The bed height compacted toapproximately 64% of the initial volume of the mixture, and theturbidity of the supernatant was 387 NTU. A sample of the grassclippings-coal solids was dabbed dry with paper towels, and theremaining wet solids contained approximately 52% dry solids. The solidscan be air dried or dried by some other means to produce readily usablefuel.

Example 16: Activated Coal Slurry+Tethered Peanut Shells, Filtration

A solution containing tethered peanut shells plus activated coal slurrysolution, all prepared in accordance with Example 11, was mixed for ˜10seconds and poured into a filtration unit with a 80 mesh stainless steelscreen. When mild vacuum was applied to the mixture, the filtrationprocess took 40 seconds. The turbidity of the filtrate was 75 NTU. Asample of the retentate (peanut shells-coal solids) containedapproximately 48% dry solids. The solids can be air dried or dried bysome other means to produce readily usable fuel.

Example 17: Activated Coal Slurry+Tethered Pulp, Filtration

A solution of tethered pulp plus activated coal slurry solution, allprepared in accordance with Example 13, was mixed for ˜10 seconds andpoured into a filtration unit with a 80 mesh stainless steel screen.When mild vacuum was applied to the mixture, the filtration process took37 seconds. The turbidity of the filtrate was 122 NTU. A sample of theretentate (pulp-coal solids) contained approximately 48% dry solids. Thesolids can be air dried or dried by some other means to produce readilyusable fuel.

Example 18: Activated Coal Slurry+Tethered Filter Cake Coal (FC) or CoalProcessing Refuse (CPR)

For each experiment in this Example, a sample of FC or CPR was used asanchors. For each sample, a dilute solution of the tethering polymer(p-DADMAC) was added at 500 ppm based on solids, and mixed. Activatedcoal slurry was prepared in accordance with Example 8. The tethered FCor CPR was added to the activated coal slurry and was gently mixed. Themixture was then gravity filtered through a filtration unit having a 80mesh stainless steel screen. The time of filtration for each sample wasmeasured starting from the time that the activated coal/tethered CPR orFC mixture was poured on the filter mesh. The solids residing on themesh were analyzed while resident on the screen, using a moistureanalyzer. An aliquot of the resident solids was blotted dry with papertowels to remove externally adherent water drops and was then analyzedto determine the dry solids content. The results of these experimentsare set forth in Table 1 below.

TABLE 1 Filtration Filtrate Dry Dry Anchor:Fines Time Turbidity SolidsSolids Sample (g:g) (s) (NTU) (%) Dabbed (%) FC-1 0.5:1 67 23 59 66CPR-1 0.5:1 152 274 60 65 CPR-2   1:1 66 20 66 79

For each sample, the solids resident on the filter mesh were compact andself-adherent. For certain samples, the solids could be easily scrapedor removed from the filter in one or two pieces. The filtrate for allsamples had low turbidity values, with samples FC-1 and CPR-2 havingextremely low turbidity values of 23 NTU and 20 NTU, respectively.

After performing the measurements above, the integrity and cohesivenessof the solid material on the filter mesh was tested by pouring a largeamount of water onto the solids resident on the mesh. Vacuum was appliedand water was refiltered through the solids. Filtration time andturbidity of filtrate were measured, and the solid samples wereexamined. For each sample, the resident solids appeared stable andcohesive. The CPR-2 sample's second filtration time was under threeminutes and the filtrate had an even lower turbidity of 8.5 NTU, whilethe FC-1 sample took 17 minutes to filter and the filtrate had aslightly higher turbidity value of 34 NTU. These experiments suggestthat the consolidated solids prepared in accordance with this protocolretain their integrity even after exposure to water washing, as mightoccur, for example, with heavy rains, and there is no evidence ofsignificant redispersion of the particles in the water.

For each sample, the remaining solids were oven-dried and examinedthereafter for consistency and cohesiveness. For each sample, a solidand apparently geotechnically stable dried mass resulted fromoven-drying.

Examples 19-27

The following materials were used in Examples 19-27 below:

-   -   Poly(diallyldimethylammonium chloride) (PDAC), 20% in Water,        Sigma-Aldrich, St. Louis, Mo.    -   Magnafloc LT30, Ciba/BASF, Ludwigshafen, Germany    -   Sand, Sigma-Aldrich, St. Louis, Mo.    -   Clay fines slurry, BASF montmorillonite (F-100).

Example 19: Basic Procedure

A clay fines suspension, shown in FIG. 3A, was prepared from a 25 wt %slurry of montmorrilonite in water made by mixing in a Silverson L4RT-Ahomogenizer at 5,000 rpm for one hour. The 25 wt % slurry was diluteddown to a 5% solids by weight of clay to simulate the clay finessuspension (tailings) produced during phosphate beneficiation. A 250 gm.sample of the 5 wt % clay fines suspension was activated by adding anamount of a 0.1% solution of Magnafloc LT30 as the activator polymer, asdetailed in the Examples below. After the activator was added, thesample was agitated by pouring it between two beakers (up to six times)to ensure good mixing. Flocs were evident following this mixing, asshown in FIG. 3B. Separately, a slurry of sand “anchor particles” inwater was prepared by adding sand to water as detailed in the Examplesbelow to produce an 85% by weight sand slurry, as shown in FIG. 4.Various amounts of 1% PDAC were added to the sand slurry as the tetherpolymer, so that tether-bearing anchor particles were produced. Theactivated clay fines and the tether-bearing anchor particles werecombined in ajar and sealed with a lid. The jar was inverted five timesto mix the two fluid streams. The contents of the jar were then pouredonto an 80-mesh screen and allowed to gravity-filter for one minute.After one minute, a sample of the filtered-out solids was analyzed on anA&D ML-50 moisture balance to determine the solids content. Theturbidity of the filtrate was also determined.

Example 20: 1:1 Sand-to-Clay

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 12.5 g of 0.1% activator polymer

Sand Stream

-   -   a. 12.5 g of sand    -   b. 2.2 g of water    -   c. 1.25 g of 1% tether polymer

The filtered-out solid sample contained 30.1% solids, and the filtratehad a turbidity of 87 NTU. FIG. 5 shows the mixed fluid streams in thejar immediately after combination. FIG. 6A shows the mixture followingfiltration, with recovered solids and clear filtrate. FIG. 6B shows therecovered solids.

Example 21: No Sand Stream

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 12.5 g of 0.1% activator polymer

(No Sand Stream)

No solids were retained on the 80-mesh screen. After settling for oneminute the supernatant had a turbidity above detection limits (>1000NTU).

Example 22: Tethered Sand, No Activator

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension

Sand Stream

-   -   a. 12.5 g of sand    -   b. 2.2 g of water    -   c. 1.25 g of 1% tether polymer

No solids were retained on the 80-mesh screen. After settling for oneminute the supernatant had a turbidity above detection limits (>1000NTU).

Example 23: Only Tether Polymer, without Sand

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 12.5 g of 0.1% activator polymer        Sand Stream: 1.25 g of 1% tether polymer alone, without        attachment to sand

The filtered-out solid contained 13.2% solids, and the supernatant had aturbidity of 13.5 NTU. Only about 10% of the generated solids wereretained on the 80-mesh screen.

Example 24: Plain Sand, No Tether

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 12.5 g of 0.1% activator polymer        Sand Stream: 12.5 g of sand

The filtered-out solid contained 27.2% solids, and the turbidity of thefiltrate was 509 NTU. Only about 5% of the solids were retained on the80-mesh screen.

Example 25: 1:1 Sand-to-Clay, Low Polymer Dosing

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 6.3 g of 0.1% activator

Sand Stream

-   -   a. 12.5 g of sand    -   b. 2.2 g of water    -   c. 0.3 g of 1% tether

The filtered-out solid contained 33.7% solids and the supernatant had aturbidity of 77 NTU. Thus it is possible with low polymer dosing togenerate solids with good solids content and clear water in thesupernatant.

Example 26: 1:1 Sand-to-Clay, Constant Activator Polymer Amount, VaryingAmounts of Tether Polymer

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension slurry    -   b. 12.5 g of 0.1% activator

Sand Stream

-   -   a. 12.5 g of sand    -   b. 2.2 g of water    -   c. 1% tether solution, at doses of about 250 ppm, about 500 ppm,        about 1000 ppm and about 2000 ppm.

The results are shown in Graph 1 on FIG. 7. At a constant activatordosage of 1000 ppm, the solids generated by using varying amounts oftether to modify the sand produce decrease in solids content above atether dosage of around 500 ppm. Turbidity values vary in a lessconsistent manner, but can still be manipulated by varying tetherdosage. This demonstrates that varying the tether dosage can improve thesolids retrieval from the clay fines stream.

Example 27: 1:1 Sand-to-Clay, Constant Tether Polymer Amount, VaryingAmount of Activator Polymer

The following materials were used in accordance with the procedure setforth in Example 19:

Clay Fines Stream

-   -   a. 250 g of 5% clay fines suspension    -   b. 0.1% activator solution, at doses of about 250 ppm, about 500        ppm, about 1000 ppm, and about 2000 ppm

Sand Stream

-   -   a. 12.5 g of sand    -   b. 2.2 g of water    -   c. 1.25 g of 1% tether

The results are shown in Graph 2 on FIG. 8. At a constant tether dosageof 1000 ppm, the solids generated by using varying amounts of activatorincrease with increasing activator dosage, but appear to level outaround by 2,000 ppm. Thus, the activator dosage can also be used as away to modulate the solids content of the consolidated clay.

EQUIVALENTS

While specific embodiments of the subject invention have been discussed,the above specification is illustrative and not restrictive. Manyvariations of the invention will become apparent to those skilled in theart upon review of this specification. Unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth herein areapproximations that can vary depending upon the desired propertiessought to be obtained by the present invention.

1. A method of removing particulate matter from a waste tailing fluid,comprising: providing an activating material capable of being affixed tothe particulate matter; affixing the activating material to theparticulate matter to form an activated particle; providing an anchorparticle and providing a tethering material capable of being affixed tothe anchor particle; and attaching the tethering material to the anchorparticle followed by attaching the tethering material to the activatedparticle to form a removable complex in the fluid; wherein the fluid isa waste tailing fluid derived from energy production or a miningprocess.
 2. The method of claim 1, wherein the mining process is coalmining.
 3. The method of claim 1, wherein the mining process is themining of an inorganic ore.
 4. The method of claim 1, wherein the miningprocess is the processing or beneficiation of an ore.
 5. The method ofclaim 4, wherein the ore is selected from the group consisting of iron,trona, phosphate, kaolin, bauxite and potash.
 6. The method of claim 1,wherein the particulate matter is selected from the group consisting ofcoal combustion products, coal fines, clay particles and mineralparticles.
 7. The method of claim 6, wherein the particulate matter iscoal combustion products.
 8. The method of claim 7, wherein the coalcombustion products are selected from the group consisting of fly ash,bottom ash, boiler slag, flue gas desulfurization material and acombination of any of thereof.
 9. The method of claim 1, wherein theparticulate matter has a mass mean diameter less than about 50 microns.10. The method of claim 6, wherein the particulate matter has a massmean diameter less than about 50 microns.
 11. The method of claim 1,wherein the fluid is selected from the group consisting of red mud fluidstream, gangue, slurry containing fine particulate kaolin, tailings fromtrona mining and slurry produced by phosphate beneficiation.
 12. Themethod of claim 1, further comprising removing the removable complexfrom the fluid.
 13. The method of claim 12, wherein the removablecomplex is removed by a process selected from the group consisting offiltration, centrifugation or gravitational settling.
 14. The method ofclaim 1, wherein the anchor particle comprises sand.
 15. The method ofclaim 1, wherein the tethering material is selected from the groupconsisting of chitosan, lupamin, branched polyethyleneimine (BPEI),polydimethyldiallylammonium chloride (PDAC), andpolydiallyldimethylammonium chloride (pDADMAC).
 16. The method of claim15, wherein the tethering material is chitosan and the activatingmaterial is an anionic material.
 17. The method of claim 1, wherein theparticulate matter comprises quartz, clay fines or a combinationthereof.
 18. The method of claim 1, wherein the activated particleattaches to the tethering material by electrostatic interaction,hydrogen bonding or hydrophobic behavior.
 19. The method of claim 1,wherein the activating material is an anionic or cationic polymer. 20.The method of claim 1, wherein the activating material is a polyanionand the tethering material is polycation.
 21. The method of claim 1,wherein the activating material is a polycation and the tetheringmaterial is a polyanion.
 22. A method of removing particulate matterfrom a fluid, comprising: providing a modified particle comprising aparticle functionalized by attachment of at least one amine functionalgroup; dispersing the modified particle within the fluid so that itcontacts the particulate matter to form a removable complex in thefluid; and removing the removable complex from the fluid wherein thefluid is a waste tailing fluid derived from energy production or amining process. 23-26. (canceled)
 27. A system for removing coal finesfrom a fluid, comprising: a fluid containing a population of suspendedcoal fines; an activator polymer added to the fluid to complex with thesuspended coal fines to form activated coal fines, the activated coalfines residing within the fluid volume; an anchor particle complexedwith a tethering agent to form tether-bearing anchor particles, thetether-bearing anchor particles being mixed with the fluid volume tocontact the activated coal fines, the tether-bearing anchor particlesbeing capable of complexing with the activated coal fines to formcomplexes removable from the fluid; wherein the complexes removable fromthe fluid comprise a composite material comprising complexed coal finesand anchor particles. 28-32. (canceled)
 33. A method for removing coalfines from a fluid, comprising: providing an activator polymer capableof interacting with a population of coal fines suspended in a fluid;adding the activator polymer to the population to form activated coalfines; providing an anchor particle; complexing the anchor particle witha tethering agent capable of complexing with the activated coal fines,thereby forming tether-bearing anchor particles; mixing thetether-bearing anchor particles with the activated coal fines to form acomplex removable from the fluid, the complex comprising a compositematerial comprising coal fines and anchor particles; and removing thecomposite material from the fluid. 34-46. (canceled)
 47. The method ofclaim 1, wherein the anchor particle comprises a material indigenous toa mining process.
 48. A system for removing particulate matter from afluid, comprising: an activating material capable of being affixed tothe particulate matter to form an activated particle; a tether-bearinganchor particle capable of attaching to the activated particle to form aremovable complex in the fluid; and a separator for separating theremovable complex from the fluid, thereby removing the particulatematter; wherein the fluid is a waste tailing fluid derived from energyproduction or a mining process.